otto robert frisch, 1 october 1904 - 22 september...

September 1979Otto Robert Frisch, 1 October 1904 - 22

Sir Rudolf Peierls, F. R. S.

1981, 283-306, published 1 November271981 Biogr. Mems Fell. R. Soc.

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OTTO ROBERT FRISCH1 O ctober 1904 — 22 Septem ber 1979

Elected F .R .S . 1948

B y S i r R u d o l f P e i e r l s , F .R .S .

O. R. F r i s c h brough t to physics the approach of a craftsm an. He enjoyed, above all, doing experim ents w ith his own hands, preferably on apparatus of his own design, aim ed at simple basic questions. T h is approach required the ability to th ink about the im portan t problem s of physics sim ply, b u t deeply, an ability underlying the two contributions for w hich he was best known: his share in the explanation of the fission process and tha t in the recognition of the feasibility of an atom ic weapon. T h e craftsm an was also som ething of an artist, not only in his love for m usic and his skill and taste as a pianist and a violinist, bu t in the use of language, w hich m ade him an outstanding expositor.

T h ere were m any problem s, in physics and elsewhere, w hich he regarded as interesting, and these he pursued persistently, in depth, until he saw convincing answers in simple term s, and he evidently enjoyed him self in doing so. H e equally firmly refused to becom e involved w ith m atters o ther than those w hich he had decided were of interest to him .

V i e n n a a n d B e r l i n

O tto R obert Frisch was born in V ienna. H is paternal grandfather, M oriz Frisch, im m igrated from Galicia, and did well as a prin ter, until generosity and a casual attitude to accounting led to bankruptcy. O tto R obert’s father, Justin ian Frisch, b rought the firm back to solvency, and later w orked for o ther p rin ting and publishing firms. H e was also a gifted painter, specializing in w ater colours. H is son’s recollections (B5) stress his wit, his firm sense of righ t and wrong, and the m any interests to which he in troduced the son, including m athem atics. I t is likely that he also passed on to him his keen sense of language.

T h e m other, A uguste, nee M eitner, was the daughter of a lawyer. She was a gifted m usician, who became a concert pianist at a very young age, and also studied com position and conducting, bu t gave up her musical

283



284 Biographical Memoirs

career when she m arried. H er sister was Lise M eitner, who became a nuclear physicist of great distinction and was to have a strong influence on her nephew.

In the family the boy was always known as ‘O tto R obert’, as if the two nam es were hyphenated. L ater he tended to call him self Robert, except at Los Alamos, w here there were too m any Roberts, and he was called O tto. T h is usage seems to have persisted; his book of recollections (B5) and some articles are headed ‘O tto F risch ’.

H e showed quite early a gift for m athem atics, and the ability to see th rough m athem atical o r logical argum ents at great speed. T h is later extended to a similar speed in seeing m echanical points. I noticed this when, about 1940, I started teaching him to drive, and at the first lesson, when he had been introduced to the gears, he started dow nhill, and shifted from first directly in to th ird gear. W hen I pointed out that this was not the usual way, he replied ‘D ow nhill th is should be all r ig h t’, as, of course, it was.

H is ability and interest in m athem atics suggested this as his m ain subject of study at the university , bu t when he did en ter the U niversity of V ienna in 1922, he felt that a career in m athem atics w ould be too dry and abstract for his taste, and he chose physics. A ustrian physics courses then had no division between undergraduate and postgraduate study, and no equivalent of the bachelor’s degree. T he first exam ination was the D r Phil., for w hich he qualified ‘ cum ’ in four years, w hich was fairly norm al. H is thesis work was done under K arl Przibram in the Institu t fur Radium forschung. on ‘V erfarbung von Steinsalz durch K athodenstrah- len’ (D iscoloration of rock salt by cathode rays).

H is first published paper (1), datelined from tha t institu te and read to the m eeting of the Vienna Academy on 27 January 1927, was related to the subject of his thesis. I t is concerned w ith the effect of slow electrons on rock salt, of interest in connection w ith the form ation of colour centres, on which Przibram was then working. T h e experim ent was difficult because of the effect of space charges on the slow electrons, and required m uch care and ingenuity. T h e findings were largely qualitative.

A fter graduating he spent about a year in a small private laboratory of a firm m anufacturing X -ray dosim eters. T h e head of the firm was an inventor, Siegm und Strauss, who liked to try out his ideas on his young assistant. ‘He was full of ideas, and it was part o f m y job to listen and throw out the dud ones’ (B5, p. 13). T h is was evidently an opportunity for practising his ability to understand and judge such points quickly, and his em ployer m ust have been aware of this ability.

In 1927 he was offered an appointm ent in the Physikalisch-Technische Reichsanstalt in B erlin-C harlottenburg, the G erm an governm ent in stitution roughly equivalent to the N ational Physical Laboratory. T he offer came as a surprise to him; it was probably due to a recom m endation from Professor Przibram . H is duties were hardly exciting. T hey were



Otto Robert Frisch 285

concerned w ith an a ttem pt to set up a b e tte r way of m easuring light intensity . A short paper, pub lished jo in tly w ith his boss (3), related to the m easurem ent of very weak cu rren ts, in connection w ith the in strum en t they w ere developing.

H ow ever, the period in Berlin was m uch m ore in teresting than the job he had to do. H e used m uch of his spare tim e to stay in the laboratory and to try ou t various ideas of his own. H e also was able to attend sem inar m eetings at the U niversity of B erlin, and to listen to the physicists there, including M ax Planck, M ax von L aue, E instein , G ustav H ertz and m any visitors. A no ther im portan t contact was Lise M eitner, w ho lived and w orked in the Berlin subu rb of D ahlem . F risch had lodgings in the same neighbourhood, although th is m eant a long bus ride to work, so as to keep in touch w ith his aun t, to the benefit b o th of his physics and his m usic.

D uring his th ird year in Berlin he was given facilities to do experim ents in the laboratory of P eter P ringsheim , originally to allow him to try an experim ent w hich was to show th a t a light quan tum can have an in trinsic angular m om entum in a transverse direction. T h e experim ent gave a negative result, and eventually Jam es Franck explained to h im tha t he had overlooked the existence of orb ital angular m om entum . N evertheless he pub lished a paper on the experim ent (5). H e explains ‘M y paper was already w ritten , and the best I could do was to add F ranck ’s explanation as a footnote’ (B5, p. 39). Perhaps the paper was already subm itted , and the explanation was added in proof, though it is no t m arked as an addition in p roof (and is no t a footnote). H ow ever, the contact w ith P ringsheim led to a tem porary grant w hen the appoin tm ent at the R eichsanstalt ran out, and jo in t work w ith P ringsheim resulted in a paper (5) w hich settled a po in t of principle w hich had been in doub t in the early application of q uan tum theory to spectroscopy.

H e left Berlin in 1930 to accept a position in H am burg.

H a m b u r g

T h e professor there was O tto S tern , a great personality and an outstand ing experim enter. T h is was not th rough m anual dexterity , w hich he seemed to be lacking, bu t th rough a brilliantly clear insight into the na tu re o f the experim ent, w hich allowed him to m inim ize, and to control, all possible sources of error. H is field was the use of m olecular beam s; he won the N obel Prize for his work w ith G erlach, w hich proved the directional quantization of atom ic angular m om enta. Since then he had, w ith his collaborators, notably I. E sterm ann, perfected the tech nique and applied it to m any im portan t physical problem s.

F risch was invited to jo in S tern as an A ssistant, a regular appoin tm ent in a G erm an university, no doubt on P ringsheim ’s recom m endation. H e took rapidly to the m olecular-beam technique, w ith all its technical intricacies. H e took part in an experim ent on the diffraction of atom s by a




crystal surface. T h is had previously been done qualitatively b yE ste rm ann and S tern , b u t for a quantita tive check on the w avelength one requ ired beam s in w hich all atom s had very nearly the same velocity, and th is was achieved by m eans of a ‘beam chopper’, a set of tw o ro tating slo tted discs, th rough w hich only the atom s of a certain speed can pass. H e reports (B5, p. 45) tha t a small discrepancy betw een the w avelength found and the theoretical de Broglie value was traced to an e rro r in the nu m b er of slots in the discs (8—10).

H e describes his role in such experim ents as S te rn ’s ‘pair of h an d s’, and this is no doub t correct in the sense th a t S tern d id no t like touching the apparatus him self, bu t one w ould guess tha t F risch played also an active part in the design of the experim ents and in considering the factors involved.

O ther work of the H am burg period (11-19) includes a study, jo in tly w ith E. Segre, of the response of atom ic angular m om enta to changes in d irection of the m agnetic field, a p rob lem w hich had been an in trigu ing m ystery for the old quan tum theory, b u t could be described by quan tum m echanics (11, 14, 15). Jo in t w ork w ith S tern reports anom alies in the specular reflection of atom ic beam s from crystal surfaces (13, 16, 17). H ow ever, the m ost im portan t finding was the discovery of the m agnetic m om ent of the p ro ton (18) w ith the surprising resu lt tha t th is was some 2 to 3 tim es larger than the nuclear m agneton p red ic ted by the D irac equation.

F risch ’s last paper from H am burg (19), and probably the last paper from the S tern group there, was ra ther characteristic of his approach. It set out to verify the pred ic tion of quan tum theory tha t an atom , on em itting a light quan tum , recoils. A t the end of the paper he com m ents tha t he had verified the m agnitude of the p red ic ted recoil only w ith lim ited accuracy and adds: ‘I t w ould undoub ted ly have been possible to obtain , perhaps w ith even narrow er beam s, substantially cleaner and less objectionable results, b u t the experim ents had to be d iscontinued for external reasons’.

T h e date of receipt of th is paper was 22 A ugust 1933, and the ‘external reasons’ were the racial laws of N azi G erm any, w hich com pelled S tern , E sterm ann and F risch to leave. H e had planned to go to Rom e w ith a Rockefeller Fellow ship w hich he had been aw arded, b u t th is becam e im possible because the Fellow ship was contingent on having a regular appoin tm ent to re tu rn to. Eventually S tern , w ho w orked hard to find posts for his displaced collaborators, arranged for F risch to jo in Blackett at Birkbeck College.

L o n d o n

D uring his stay in L ondon he was m aintained by a gran t from the A cadem ic Assistance Council, set up to provide help and tem porary




support for displaced scholars. T h is was done in a sp irit of im pressive generosity, com ing at a tim e of econom ic depression and a shortage of academ ic posts, particu larly as m uch of the initiative cam e from the academ ics, w ho m igh t well have been expected to fear the com petition of so m any new com ers.

B lackett’s laboratory d id no t have the equ ipm en t for m olecular-beam research, and F risch jo ined in the w ork of the laboratory , in w hich the cloud cham ber was the dom inan t tool. H e set h im self the task of developing a cloud cham ber w ith a long acceptance tim e. H e succeeded in constructing th is (21), b u t it was never used as a research tool.

A t th a t tim e artificial radioactivity had been discovered by the Joliot- C uries, and several m em bers of the laboratory took up th is new line of study . F risch jo ined them . H e realized tha t there m igh t exist some very short-lived activities, w hich could be detected only by m oving the sam ple very rapidly from the a -ray source to w hich it had been exposed, to the vicinity of a counter. W ith his love for gadgets he soon had m ade a m echanical device for achieving this, and w ith it he discovered two new radioactive isotopes, though no t particu larly short-lived.

H e d id no t really settle dow n at B irkbeck College, w here his stay clearly w ould be only tem porary . B ut it was an oppo rtun ity to broaden his outlook, to make new friends, and to m ake his first acquaintance w ith life in E ngland, w here he w ould spend later so m uch of his life.

In the sum m er of 1934 N iels B ohr invited him to jo in his In stitu te in C openhagen.

C o p e n h a g e n

N iels B ohr’s In stitu te of T heoretical Physics had, in spite of its nam e, a long trad ition of experim ental work, and there was in terest in nuclear physics, w here F risch ’s recent experience and skill could fit in well. T h is was the first appoin tm ent w hich he was able to keep for a long tim e, and he soon felt at hom e there. T h e atm osphere in the Institu te , w ith its un ique position in m odern theoretical physics, and a first-rate group of experim entalists, was stim ulating, and he m ade m any friends. H e becam e quite proficient in D anish , at least in speaking; he com plained tha t understand ing the rapidly spoken w ord rem ained difficult (B5, p. 84). H e liked to speculate tha t the peculiar sound of D anish , dom inated by vowels, w ith the consonants m ostly swallowed, developed from the shouts of seam en from boat to boat to com m unicate du ring a gale. Like m ost people who had been in B ohr’s Institu te , he always retained a special affection for the In stitu te and for Copenhagen.

A t first he continued the type of w ork he had started in London, discovering two m ore radioactive isotopes (22). T h en there was a new excitem ent in nuclear physics w hen Ferm i showed how m uch could be learn t by studying the collisions of neu trons w ith nuclei. T h e new



approach was taken up vigorously in Copenhagen, and Frisch took part in it. T h e next ten papers on the list (23—32) contain the results of this activity.

A t tha t tim e there was no way of m easuring the energy of a neutron , or producing m onoenergetic beam s, so the exploration of this new and com plicated field of physics had to proceed as if one studied the optical p roperties of m aterials w ithout a spectroscope, ju s t using filters whose characteristics had to be deduced from the results. T h is exploration was carried out in m any laboratories, whose results som etim es duplicated, bu t m ore often inspired and supplem ented each other. I t w ould take a specialized study to ascertain the im portance and im pact of the contribu tions of any one person or group, bu t it is clear tha t the Copenhagen work, and F risch ’s experim ents in particular, had an im portan t place in th is exploration.

T hese papers are characterized by the im aginative use of experim ental techniques and by a choice of problem s relating directly to fundam ental issues. T h e relation to o ther parts of physics was not overlooked, as, for exam ple, in a paper (28) w hich asks w hich of the M axwell quantities, B or H, is probed by a neutron passing th rough m agnetized iron.

M uch of this work was done in collaboration w ith H . von H alban, who pursued neu tron physics w ith his trem endous energy and sense of urgency, and G. Placzek, a m an of great b read th of in terest and erudition, at hom e both in experim ental and theoretical physics, a rem arkable character described in F risch ’s recollections (B5, pp. 81—84) w ith hum our and affection.

In all this jo in t work F risch seems to have been landed w ith the more onerous tasks, such as grinding beryllium into a fine pow der for the a-Be neu tron sources. P resum ably the reason was tha t he was good at doing such rough m echanical jobs, and was willing to do w hat was necessary.

It was a great experience for him to w atch Niels Bohr resolve the paradox of the large absorption cross sections of nuclei for neutrons and the sharpness and closeness of resonances by his picture of the com pound nucleus, w hich after its publication in 1936 dom inated m ost of the th inking about nuclei.

A nother great discovery w hich shook nuclear physics was the discovery of fission, in w hich Frisch became closely involved. H e was spending C hristm as 1938 w ith Lise M eitner, who, after being dism issed from her job at the K aiser-W ilhelm Institu te in B erlin-D ahlem , had settled in Stockholm . She received a letter from O tto H ahn, w ith w hom she had collaborated during m ost of her career, reporting that one of the products of the collision of neutrons w ith uran ium was barium , an elem ent of about half the atomic w eight of uranium , rather than the transuranic elem ents Ferm i had thought he had form ed by neu tron capture in uranium . H ahn concluded that this m ust m ean that the uran ium nucleus had split into two large pieces.





Frisch and Lise M eitner discussed this apparently incredible in form ation. T h ey began to realize tha t th is m ust be due to the m utual electrostatic repulsion of the charges in the nucleus, w hich tries to drive the nucleus apart, w hereas the surface tension tends to hold it together. If by an external influence, such as the im pact of a neu tron , the shape of the nucleus becom es d isto rted , becom ing elongated instead of spherical, the electric forces can becom e dom inant, and the nucleus will split. F risch suggested the te rm ‘fission’ for th is process. T hey also estim ated the energy acquired by the fragm ents as a resu lt of the repulsion, and found the staggeringly large figure of 200 M eV for the total energy. T h is agreed, in order of m agnitude, w ith the energy difference, com puted from the m ass defect, betw een a u ran ium nucleus and two nuclei of about half the mass.

T hese conclusions were w ritten up in a le tter to N ature (33), w hich has becom e a classic. Its final text was drafted over the telephone after F risch had re tu rned to Copenhagen. I t was shown to Bohr ju s t as he was leaving for a visit to the In stitu te for A dvanced S tudy in Princeton.

F risch decided* to try proving the in terpreta tion of the process by detecting the fission fragm ents, and it took him only two days to do so, since the great ionizing pow er of the heavy fragm ents makes them very easy to detect and to identify. H e recalls (G60) tha t ju s t as he com pleted the experim ent, he received a telegram announcing that his father had been released from a G erm an concentration cam p and w ould be able to jo in him . T h e experim ent was also reported in a le tter to N ature (34), sent off jo in tly w ith the o ther one. I t was five weeks before they were published, about the norm al delay at the tim e. If Bohr had been in Copenhagen he could no doub t have persuaded the editor to give these le tters some priority .

M eanw hile the news of the fission process was causing a sensation also in Am erica. Bohr reported to a m eeting w hat he knew, and also the paper by H ahn and S trassm ann about the ir experim ents arrived in the U .S .A . Several physicists, unaw are of F risch ’s experim ent, looked for, and found, evidence of the fission fragm ents them selves. Because of some m isunderstandings F risch ’s finding was not im m ediately reported to Bohr, who becam e very concerned tha t Frisch and Lise M eitner m ight not be getting the recognition they deserved.

In retrospect, there is no doub t tha t F risch was the first to show experim entally the existence of the fission fragm ents. However, this priority in tim e by a small m argin should probably not be taken too seriously w hen several others did sim ilar experim ents shortly afterw ards quite independently . T h ere is no question about the im portance of the note by M eitner and Frisch, w ith its clear discussion of the physics of the

* According to one account (G60) the experiment was started immediately after his return from Stockholm. In the book (B5, p. 117) he says that this was only after Placzek had queried the M eitner-Frisch interpretation of the Hahn—Strassmann experiment and asked for a direct proof.



fission process in sim ple term s. I t is an indication of the im pact of this note tha t the te rm ‘fission’ proposed in it im m ediately becam e accepted as the nam e of the new process.

D uring a subsequent visit of Lise M eitner to C openhagen, she and F risch perform ed experim ents about the nature of the fission products, and showed the wide range of half-lives am ong them (35, 36). Frisch proposed a sim ple em pirical form ula for the tim e dependence of the activity, resulting from a practically continuous d istribu tion of half-lives (37).

By now external events had again d istu rbed the peaceful and p ro ductive way of life in Copenhagen. G erm any had annexed A ustria, and F risch had thereby becom e a G erm an citizen. W ar was clearly im m inent, and one could foresee tha t in a war D enm ark was likely to be occupied by the G erm an forces, and this w ould make it a very unsuitable place for a ‘N on-A ryan ’ em igre. Besides, the D anish police w ere beginning to make difficulties about renew ing F risch ’s perm it, though he did not know this.

H e had come to the conclusion tha t he w ould like to re tu rn to England, and m ade this desire clear to every visitor from England. In the end O liphant responded w ith an invitation to B irm ingham .

B i r m i n g h a m

H is trip to B irm ingham was in tended as a sum m er vacation, in w hich the possibility of staying there w ould be explored, and if it worked out he w ould re tu rn to Copenhagen for his belongings. H owever, during his stay the war started , and it w ould have been unwise to retu rn , since, as a G erm an citizen, he m ight no t be allowed to en ter G reat B ritain again. So he stayed, and his Copenhagen friends had to pack up his m ost essential belongings, vacate his flat and dispose of his half-paid-for piano. M eanw hile one of the B irm ingham physics staff had left, so F risch could be given a tem porary appoin tm ent as a teaching assistant. T h e teaching duties did no t occupy much* of his tim e. T h e physics departm ent was developing an in terest in nuclear physics, bu t there was as yet little equipm ent. O liphant and m any of his collaborators were busy w ith radar research, in w hich foreigners were not allowed to participate.

H is in terest was still focused on the fission problem . By this tim e Niels Bohr had applied his ideas on nuclear reactions to the analysis of this problem , and had concluded that the observed slow -neutron-induced fission was entirely due to the rare isotope 235U . T h is was com forting, because of the discovery tha t in the fission process secondary neutrons are em itted. If these can in tu rn cause fission the result may be a chain reaction. Because of the huge am ount of energy this could release, it suggested the possibility of a new and devastating weapon.

B ohr’s analysis, elaborated quantitatively in his paper w ith W heeler (1939), im plied that no explosive chain reaction was possible in natural





uran ium . F risch was convinced by B ohr’s argum ents, b u t w anted to verify the assignm ent to th e light isotope. F o r th is purpose he tried to set up equ ipm en t w hich could separate the isotopes, o r at least vary the com position. I t appeared th a t the best m ethod for th is, and the only one tha t could be a ttem p ted w ith sim ple equ ipm ent, was therm al diffusion, am plified in a counter-flow colum n first used by C lusius and Dickel. By a coincidence, one of the m ost senior m em bers of the B irm ingham departm en t, D r T . L . Ibbs, was one of the w o rld ’s experts on therm al diffusion, b u t F risch d id no t know th is at the tim e. T h e experim ent came to no th ing because for U F 6, the only know n gaseous u ran ium com pound, the therm al diffusion coefficient, w hich depends on the in term olecular forces, happens to be practically zero. H ow ever, he rem ained p re occupied w ith though ts about fission and its im plications. T hese though ts w ere fu rth er s tim ulated by his having to w rite an article about the subject.

T h e annual reports of the C hem ical Society contained a section on nuclear physics, and F risch and I had been asked to w rite this for the cu rren t volum e. N atura lly the part on the experim ental situation, and on fission, fell to h im (38). H is repo rt included the conclusion th a t there was no possibility of an explosive chain reaction.

B ut fu rth er reflection, stim ulated by his in terest in isotope separation, set h im w ondering w hat w ould happen if one could obtain a substantial quan tity of pure 235U . H e raised th is question in conversation w ith me, because I had recently w orked ou t a form ula giving the critical size for a chain reaction no t involving the slow ing-dow n of neutrons. I had been doub tfu l about the p roprie ty of pub lish ing such a calculation, b u t F risch had convinced me tha t a w eapon was no t a practical possibility, and I sent the paper off for publication.

So now we tried to estim ate the critical size of a sphere of 235U . B ohr’s analysis suggested tha t the fission cross section of this nucleus for fast neu trons should be about as large as the geom etrical cross section, since fission w ould dom inate over scattering and capture. T h is tu rned out later to be an overestim ate, b u t since we had assum ed a bare u ran ium sphere w ithou t a reflector tha t w ould scatter back some of the escaping neutrons, our estim ate of ‘about a p o u n d ’ was no t too far out. T h is was m uch sm aller than one w ould have guessed. N ext we tried to estim ate how m uch of the chain reaction w ould proceed before the heat generated w ould drive the u ran ium apart, and found tha t a substantial fraction of the available fission energy w ould be released.

T h is seemed an im portan t enough finding to com m unicate to people in authority , and we w rote a m em orandum , divided into a technical and a general part (40), w hich, w ith O lip h an t’s help, was passed on to S ir H enry T izard . T h is led to the w ork of the m a u d Com m ittee, and later to the work of the T u b e Alloys project. (Both nam es were ju s t cover nam es for atom ic energy.)




F rom then on F risch spent m ost of his tim e on problem s related to atom ic energy. I t was incongruous tha t, as a G erm an citizen, and therefore an ‘enem y alien’ he should be w orking on such an im portan t and very secret project. In fact at first objections were raised, and it was suggested tha t he (and I, for tha t m atter, though I had ju s t becom e naturalized) should no t be allowed any contact w ith the fu rth er developm en t of the work, b u t th is was abandoned after a short tim e.

O ne of the m ost u rgen t problem s on the nuclear side was to check the guess about the fission cross section of 235U . Since no sam ple enriched in th is isotope was available, F risch set up a source of photo neu trons from bery llium of an energy too low to cause fission in the abundant isotope 238U . T h e rate of fission caused by these was low and hard to m easure, b u t by counting continuously for 36 hours he d id get an estim ate w hich was lower than had been expected, showing tha t our guess had been som ew hat high.

B ut carrying ou t these and o ther experim ents in the B irm ingham departm en t was not easy, as the facilities and the technical staff were fully em ployed on urgen t radar work. So F risch m oved to L iverpool in A ugust 1940.

L i v e r p o o l

H e was m ade welcom e by Professor (later Sir Jam es) Chadw ick in his laboratory , and F risch w ent to w ork on assorted problem s. Some work was concerned w ith the nuclear cross sections relevant to the u ran ium chain reaction, b u t he also designed an in strum en t to m easure the isotopic com position of a u ran ium sam ple by exam ining its a -ray spectrum . H e also re tu rned to the a ttem pt to separate the isotopes by gaseous therm al diffusion, and confirm ed tha t for u ran ium hexafluoride th is cannot be done.

H e m ade m any new friends in the laboratory, including Joseph R otblat, G . Pickavance and J. H olt. Life in w artim e L iverpool was not very com fortable; there were frequen t air raids. In addition, the city was in an area proh ib ited to enem y aliens, and he needed a special dispensation; another special perm ission was needed to ride a bicycle, and to be ou t of doors late at night. Even so he could no t avoid breaking the rules occasionally, bu t no trouble resulted. H e accepted all these com plications w ith good hum our, and his account of his L iverpool experiences (B5, pp. 133—147) reads like tha t of a hilarious adventure.

H e rem ained in L iverpool un til late in 1943, w hen it was decided to d iscontinue w artim e work on atom ic energy in B ritain and to transfer m any of the scientists engaged in this work, including Frisch, to the U n ited States to w ork w ith the M anhattan D istric t of the A rm y on the A m erican atom ic w eapons project. H e could not very well go there as an enem y alien, and steps were taken to make him a B ritish subject. T h is




w ould norm ally have been a p ro trac ted operation, bu t in this case bureaucracy proved its ability to m ove fast. H e had to apply for naturalization, the application had to be gran ted by the H om e Secretary, a certificate had to be issued, and w ith it he had to take the oath of allegiance, he had to register for N ational Service, and have his service deferred , a passport had to be issued, on w hich he needed a U .S . visa and an exit perm it, and finally he had to be booked a passage on a boat and sail. All th is was com pleted in 48 hours. P robably this could no t have been achieved w ithou t M iss Vera M ayne, the secretary to the d irector of T u b e Alloys, who took charge of the logistics, and despatched a breathless F risch to the various offices in the righ t order.

L os A l a m o s

T h e A tlantic crossing, in the com pany of m any o ther physicists about to jo in in the A m erican work, was slow because the unescorted liner took a zig-zag course to evade the G erm an subm arines, b u t eventually the party reached the U nited States, and F risch was assigned to the group w hich was to w ork in Los Alam os. H ere he d id no t im m ediately jo in any particu lar project, b u t acted as a general adviser and trouble-shooter. W ith his experience and ingenuity in m any techniques of nuclear physics, particularly concerning ionization cham bers (to w hich he had m ade im portan t contribu tions, including the ‘F risch g rid ’, w hich is still in use), he was able to give extrem ely valuable help in this way.

A very characteristic idea of his was to ‘m ock u p ’ the scattering of neu trons in a u ran ium block of com plicated shape, a problem relevant to bom b design, by using the scattering of light in a partially absorbing mass of perspex of corresponding shape. T h is could have been used to check the theoretic ians’ calculations, w hich for general shapes were no t too easy. In the end the procurem ent of the necessary transparen t plastic w ith absorp tion took too long, and m eanw hile enough confidence in the calculations had bu ilt up , so the project was abandoned.

As m ore 235U and p lu ton ium became available, checks on neu tron m ultip lication and determ ination of precise critical sizes becam e possible, and F risch took charge of this work. I t m eant w orking w ith near-critical assem blies of fissile m aterial, i.e. w ith an am ount ju s t not enough to sustain a chain reaction. T h is type of experim ent required extrem e care, because any unplanned m ovem ent of part of the fissile m aterial m ight push the assem bly past the critical point, and start a disastrous chain reaction. T here were later to be two fatal accidents in this work, both caused by experts being carried away into m aking changes in the procedures on the spur of the m om ent, w ithout adequate foresight. Even F risch had a narrow escape w hen he was w orking w ith a bare mass of fissile m aterial (appropriately code-nam ed G odiva) w ithout a su rround ing scatterer. As he ben t over the specim en, slow neutrons scattered back




from his body added sufficiently to the m ultip lication factor to pass criticality . O nly his alertness in observing the behaviour of the ind icator lights a ttached to the counters, and a quick reaction in pu lling away part o f the fissile m aterial, stopped the chain reaction reaching a dangerous rad ia tion level.

T h e m ost daring experim ent of th is k ind was the ‘d ragon ’, so called because it was like tickling the tail of a dragon. T h e idea, p roposed by F risch , was to have a piece of fissile m aterial w hich, because of a hole th ro u g h its m iddle, was sub-critical. A plug, w hich fitted loosely in the hole, w ould m ake it supercritical. T h e p lug was d ropped th rough the hole from a suitable height, so th a t it passed th ro u g h rapidly. T h e system w ould th u s becom e supercritical for a b rie f interval, and du ring th is tim e a chain reaction w ould develop b u t w ould no t have tim e to bu ild up to a dangerous level. F risch said he was som ew hat su rp rised to be given approval for th is experim ent, w hich was carried ou t safely and provided valuable inform ation.

W ork at Los A lam os was done w ith great urgency, as is natu ra l for w ork in w artim e on a w eapon th a t could be decisive for the outcom e of the w ar. Y et there was some spare tim e, and opportun ities for m eeting old friends and m aking new ones. In the strange scien tists’ tow n betw een the desert and the m ountains of N ew M exico, everything was a new experience to him : the clim ate and the beautifu l landscape, the log houses rem ain ing from the fo rm er board ing school and the tem porary A rm y housing , the m ilitary policem en at the gates of the tow n and of the laboratories, the Ind ian m aids and the S pan ish-A m erican technicians and labourers. B ut the feature w hich seem s to have struck h im m ost was the n u m b er of em inen t scientists and intellectuals, som e of them old friends and colleagues, w hich had gathered in th is unusual com m unity . I t was no t long before he had found congenial com pany for m aking m usic. H e was certain ly appreciated as a m usician , and during one m usical evening the rem ark was overheard: ‘T h is guy is w asting his tim e doing physics!’

H e played the piano for the local radio station of the Los Alam os com m unity , though for security reasons, as these broadcasts m igh t be overheard outside, his nam e could no t be m entioned and he was sim ply ‘our p ian ist’.

T h e re was tim e for walks in the hills (and for getting lost on the mesas w here one was ap t to be stopped by an unfam iliar canyon); there was tim e for resum ing driv ing lessons, though no t w ithou t som e em barrassing incidents. In spite of the prom ising start m entioned earlier, he was never too com fortable driv ing a car w ith m anual gear shift, because, as he com m ented later, he was too m uch aware of the m echanical operations, and th is d istracted him from the driv ing p roper. T h is difficulty was lessened w hen au tom atic cars becam e available, b u t he never took m uch to driving.




A lthough the w ork of Los A lam os was done ra ther inform ally, a project of such size requ ired m eetings and discussions from tim e to tim e, and here, w hen others w ould idly ‘doodle’ on the papers in fron t of them , F risch indulged in his hab it of draw ing portra its of those around him . T hese sketches, o f w hich som e are reproduced in his autobiography (B5), show considerable ta lent, perhaps inherited from , or inspired by, his father. M any of them b rin g ou t the personality of the subject very vividly, often by exaggerating the m ost characteristic features.

A fter the end of the w ar there was a general exodus from Los Alamos, as m ost of the scientists re tu rn ed to th e ir hom es and to the ir norm al occupations. Before leaving, the B ritish contingent decided to give a large party in appreciation of the hospita lity they had been show n. T h is included a play on local them es in the style of an English pantom im e, in w hich F risch was a great success in the part of an Ind ian m aid.

H e was invited to jo in the new A tom ic Energy R esearch E stab lishm ent at H arw ell.

H a r w e l l

H e re tu rned to E ngland early in 1946, to becom e the head of the N uclear Physics D ivision of A .E .R .E ., H arw ell. W hile the buildings at the form er airfield w ere being adapted for the ir new use, he visited the Chalk R iver L aborato ry in C anada to acquaint h im self w ith some of the problem s of nuclear pow er, and then , for a w hile, had to w ork in the L ondon office un til H arw ell becam e useable.

H e occupied him self du ring th a t tim e w ith an am bitious calculation of the statistical fluctuations in chain reactions, w hich are im portan t for accurate m easurem ents of the m ultip lication factor, and for problem s of reactor control. H e describes th is as ‘the m ost am bitious project in m athem atical physics I have ever tack led’ (B5, p. 196) and com m ents tha t it ‘later got published w ith so m any m istakes tha t I do n ’t dare look at it and certainly never tell anybody w here to find i t ’. An in ternal H arw ell report on th is subject is indeed hard to find. O f a jo in t paper w ith D . J. L ittler, published later (48), there exists a typed copy on w hich he w rote ‘Full of e rro r’. A ccording to S ir D enys W ilkinson, these calculations about fluctuations tu rned out to be useful also in understanding the behaviour of p roportional counters, and w ere helpful in determ ining the op tim um m ode for using such a counter (W ilkinson 1950).

H e used his influence to create in the laboratory an inform al a tm osphere resem bling tha t of a university laboratory. H e recalls (B5, p. 198) tha t he found tha t m ahogany benches had been installed in the laboratories, and proceeded to drill holes in them at random , to encourage people to use them as real work benches.

H e was not very in terested in the adm inistrative work of running the division, and says (B5, p. 197) tha t he occasionally apologized to D r (now



Sir R obert) C ockburn, his deputy , th a t he let h im do all the adm inistra tion . H e adds ‘B ut I th ink he enjoyed th a t.’ C ockburn certainly had greater ability as an adm inistrator.

C ockburn describes th is period in a le tter to the au thor. H e had to struggle w ith the problem of acquiring a background know ledge of nuclear physics after having concentrated for years on radar. F risch, he says,

‘soon presented m e w ith a golden key. “ Ju st express energy in term s of the de Broglie w avelength, and all your radar equations are im m ediately applicable.” T h is was typical of his approach. H e w ould sit for hours apparently day-dream ing and then give a beautifully sim ple descrip tion of some com plicated nuclear relationship. H e once told me tha t he had solved the tw elve-penny problem very easily by th inking in four dim ensions! . . . T h ere w ere endless com peting w orking parties try ing to establish a coherent program m e of re search, and O tto was no t alone in finding these tedious. I have know n h im to go to a m eeting chaired by Cockcroft o r Skinner, and decide after five m inutes tha t it was of no in terest to h im and p u t his head on his arm s and doze off. I t fell to m e to m anage the division by default. I t was no t tha t I liked it; b u t tha t he d id n ’t. I t was no t an onerous task .’

C ockburn also com m ents about F risch ’s autobiography: . . . he never m akes a harsh com m ent about anybody. H e was com pletely im pervious to the intellectual squabbles and pow er struggles rum bling all around him . H e was a true scholar, com pletely at hom e in his subject. H is particu lar ta len t was to ponder un til he could p resent a problem in a form tha t adm itted of a solution, the m ark of a real physicist.’

D uring the H arw ell period F risch also started to develop his ta len t for the popularization of science. Before leaving Los Alam os he had contrib u ted an article on ‘T h e tools of nuclear physics’ (G l) to a popular account of atom ic energy, and at H arw ell he com pleted his book M eet the atoms (B l), w hich he had started before the war.

H e rem ained at H arw ell less than two years. In 1947 he was offered the Jacksonian Professorship of N atural Philosophy in C am bridge. H e took a little tim e to make up his m ind, being a little awed by the status of the post, and by the nam es of the d istinguished predecessors, in w hich he m istakenly included R u therford (B5, p. 202).

C a m b r i d g e

C am bridge had once been one of the great centres for nuclear physics. A fter the death of R u therford in 1937, and his succession by W . L. Bragg, the em phasis in the Cavendish L aboratory shifted to o ther fields, in w hich the laboratory la ter did work of great distinction. N uclear physics





w ent in to a decline, a lthough there w ere still a n u m b er of excellent nuclear physicists on the staff. O ne sym ptom of th is decline was tha t after the w ar, w hen m any o ther un iversities w hich w ere active in nuclear physics started to bu ild large nuclear accelerators, the C avendish was no t able to a ttrac t financial su p p o rt for such a developm ent.

T h e appo in tm en t to the Jacksonian C hair of a d istinguished nuclear physicist aroused in m any m inds the hope th a t he w ould re-bu ild nuclear physics in C am bridge, and becom e the leader of a new strong group in th a t field. T h is th o u g h t m ay even have been in the m inds of the E lectors w ho appoin ted F risch to the chair. Such hopes w ere bo u n d to be d isappoin ted , because it was no t in his character to be a leader. H e was no t the k ind of person to fight for resources and grants, and to p lan the provision of b ig m achines, w hich in any case w ere no t his favourite tools. T o the nuclear physicists in th e C avendish it cam e as a surprise w hen, on one of his first days in the laboratory , he was observed queueing a t the stores for p arts for some gadget he w anted to bu ild , instead of going around scattering b rillian t ideas. N o d oub t he becam e aware of these expectations, and th is im posed som e strain on his enjoym ent of the w ork in the C avendish.

H e d id enjoy being there. H e appreciated the h igh quality of the research and its b read th , and the presence of en thusiastic and b righ t studen ts. F o r underg raduates his lectures seem to have been difficult, because he expected them to th ink too m uch for them selves. B ut for g raduate s tuden ts his ability to find sim ple p ic tu res and analogies, and his insistence on sim ple explanations m ade his lectures attractive and inspiring. D r A lan Oxley rem em bers the verse: ‘If ever you’re troub led by nuclear parity , O ld F a th e r F risch will explain it w ith c larity .’

Soon there was a group of research studen ts who looked to h im for insp ira tion , and to w hom he com m unicated some of his a ttitude to physics and to experim ents. H is tendency was, once a s tu d en t’s problem was defined, to let him get on w ith it and no t to in terfere in the details. T h is m eant som etim es tha t the s tuden t had to struggle on his own w ith obstacles, b u t tha t is a good way of learning.

H e preferred to keep the num ber of collaborators m odest. In a le tter to Bragg (who was in hospital) in O ctober 1962 he w rote: ‘T h is is a very busy te rm for me; I am giving for the first tim e a course ‘In troduction to wave m echanics’ . . . ‘F o r th is course he had studied the h istory of the discovery of the electron. H e goes on: ‘M y group at the lab. has becom e too large: w hen we have tea I can no longer talk to all of them at once (m ore than a dozen)’. M any of his students re tu rned to C am bridge in 1974 to celebrate his seventieth b irthday .

M ost of his own w ork followed his in terest in in strum entation . H e had probably been the first to realize the im portance of a pulse analyser (colloquially know n as ‘k ick-sorter’). T h is is a device w hich registers pulses from an ionization cham ber, or la ter from a scintillation or solid-




state detector, sorting them according to size, instead o f the m ore p rim itive m ethod of using a single record ing device ad justed to accept only pulses of a certain size, w hich th en has to be used m any tim es to ob ta in a com plete spectrum of pulse sizes. H e had found the need for th is in the L iverpool days in the course of developing his m ethod of testing the isotopic com position of u ran iu m sam ples by m easuring the d is tr ib u tion of a -ray pulses (42).

A t th a t tim e the p rob lem was solved by an appara tus contain ing a few dozen valves, and th is adven ture in to technology seem ed qu ite app ro pria te in the context of the large w artim e pro ject. B ut for the everyday use of the nuclear physicist he p referred som eth ing sim pler, and he designed, w ith the help of his collaborators, a m echanical device in w hich each pulse pro jected a steel ball diagonally up an inclined plane, w ith an im pulse depending on the s treng th of the pulse. T h e parabolic pa th then follow ed by the ball b ro u g h t it in to one of 30 channels, so th a t each channel collected the balls corresponding to a particu la r pulse height. T h e p a tte rn of balls therefore gave a h istogram of pulse sizes (47).

G . G . S carro tt, w ho developed the electronics for the kick-sorter, com m ents: ‘I cam e to respect his form idable ingenuity . F o r exam ple, he was responsible for the design of the parallel m otion suspension system for the cue th a t pro jected the steel balls and the elegant techn ique for m inim izing ball bounce by the use of a th in lam ina dam ped by grease on the reverse side. H e even w ound the m oving coil him self, so th a t he p u t its precise specification in the p ub lica tion .’

T h e device w orked well, and was m uch adm ired . W ith its lim ited speed and accuracy it was, how ever, hard ly m ore than a toy. Soon in strum en ts serving the same purpose by purely electronic m eans becam e available, and cam e into general use. B ut it is likely th a t F risch deserves the cred it for recognizing the im portance of such a device at an early stage.

L ater, w hen the developm ent of h igh-energy physics led to the ex tended use of bubb le cham bers, and therefore to the laborious w ork of analysing tracks in b u bb le -cham ber pho tographs, he becam e in terested in the problem of devising sem i-autom atic m ethods for th is purpose. O ne such design was described in a jo in t pub lication w ith A. J. O xley in 1960 (54).

F risch was no t satisfied w ith the speed th a t could be achieved w ith it, and decided tha t, by using a laser beam to scan the photographs, one could do better. T h e resu lt was a m uch faster m achine, to w hich he gave the nam e ‘Sw eepnik’ as its jo b was to sweep ou t the tracks, and its speed was rem iniscent of the Sputn ik . I t was first described in a paper w ith J. D avies and B. S. B. S treet in 1969 (58). T h e success of th is m achine m ade it suitable for p roduction on a com m ercial scale, and we shall re tu rn to tha t part of the story.

By this w ork on the design and use of such in strum en ts he d id , after all,




co n trib u te to m aking the C avendish a cen tre for m odern partic le physics. T oday , as the fro n t line of research shifts to ever h igher energies, the necessary accelerators have becom e too large for any un iversity laboratory , and research is done in large centres, such as C .E .R .N . or the F erm ilab ., by large team s com prising m em bers of m any laboratories. M uch of th is w ork involves bub b le cham bers, and the analysis of the p h o tog raphs is shared betw een the various groups. T h e presence of track -m easu ring devices and of physicists experienced in superv ising th e ir use and u n d ers tan d in g in sim ple te rm s th e significance of the data is therefo re essential for partic ipa tion in th is w ork. L a te r he encouraged the developm ent of a co u n ter g roup for partic le physics, though he never becam e closely involved h im se lf in the physics of th is field.

T h e re w ere occasional excursions in to o th e r fields of physics, such as the w ork w ith D . N . O lsen (50, 51) d u rin g a sabbatical v isit to C ornell U n iversity on coheren t b rem sstrah lung .

H e also re tu rn ed to his o ld field, th e m olecular beam , and u n d er his gu idance tw o studen ts, H . Bellam y and K . S m ith , set up appara tus w ith w hich to m easure nuclear spins.

H e was still in trig u ed by m echanical p roblem s. A ccord ing to K . F . S m ith ‘A t one tim e he devised a m ethod of suppo rting a horizontal p la tfo rm th ree feet above the floor w ith six legs, all o f them in com pression , sticking ou t in various d irections w ith ball and socket jo in ts at each end to give good m echanical stability . H e had a m odel m ade, w hich he used to keep on his desk in full view of any v isitor w ho m igh t be in the room w aiting for h im . M any tim es I have gone in to the room w ith R obert to find the v isitor on his knees h u n tin g around on the floor for the ball bearings and the legs, for the slightest vertical d isp lacem ent of the p la tfo rm in the m odel resu lted in a com plete collapse of the system . T h e full-size system was b u ilt and used for a tim e, b u t we w ere never able to learn w hich legs to leng then in o rder to m ove the p la tfo rm in a particu lar d irec tion— no r could R obert!’

M uch of his energy w ent in to the exposition and popularization of physics. H is special ta len t for th is had becom e obvious, and his early w ritings of th is k ind (B l, G l) had been successful. H e com m ents (B5, p. 192) th a t none of his w ritings have becom e best sellers. ‘I enjoy w riting and always get a little b it o f fan m ail w hich m akes m e feel good, and I tell m yself th a t if ju s t a few youngsters are a ttrac ted to physics by one of m y books and becom e good scientists then it was well w orth w ritin g .’

Besides his four popu la r books on physics, he w rote num erous review articles and com m ents in tended for physicists (38, 39, 41, 44, 49, 52, 53, 55—57, 59, 61) and ed ited ‘ Progress in N uclear Physics' (E l) . H e also w rote m any articles for the in telligent laym an ( G l—G 68). Perhaps the m ost often quoted , and certain ly the m ost often rep rin ted of these, is the hum orous article ‘O n the feasibility of coal-driven pow er sta tions’ (G 19) w ritten originally for a sm all house jo u rn a l circulating at H arw ell, w hich




m akes fun of the opposition to nuclear pow er by p re tend ing th a t the use of coal was to be in troduced as an innovation.

T h e great variety of jou rnals in w hich these articles appear, illustrates how m uch he was in dem and. T h e list, w hich is p robab ly no t com plete, does no t of course include lectures, b roadcasts (except those p rin ted ) or television program m es.

W hen the Sw eepnik had proved itself, it was decided to set up a firm to m anufacture and sell th is m achine. Laserscan L td was incorporated in 1969, w ith F risch as chairm an of the board (he m odestly says ‘as the o ldest’, B5, p. 218). H e rem ained chairm an un til his death. A fter his re tirem en t from his un iversity chair in 1972 he con tinued doing research in the firm , and con tinued con tribu ting new ideas to the sophistication of th e ir p roducts, including the holographic ‘zone p la te ’, w hich has since found o ther uses in add ition to those in track scanning.

In the chair at m eetings he was hard ly the conventional type of business m an; he is even know n to have d ropped off to sleep during particu larly un in teresting business. B ut he was regarded w ith deep affection by everyone in the firm .

H e m ain tained m any o ther in terests besides the w ork for Laserscan. O ne of the problem s he w orried about was the desirability of nuclear pow er. T hese though ts w ere s tim ulated by the views of his old friend, Lew K ow arski, w ho had com e to the conclusion th a t there should be a m ora to rium on bu ild ing any fu rth e r nuclear pow er stations. F risch realized the im portance of the problem , b u t found it difficult to form his judgem en t. In general, h is feeling was th a t his ability lay in explaining the facts to people by way of background, ra th e r than try ing to influence the ir views. B ut he needed to m ake up his ow n m ind , and he in tended to get rid of som e of his com m itm ents so as to have m ore tim e to th ink about such basic problem s. B ut the un fo rtunate accident w hich led to his death happened before he had im plem ented th is resolution.

L i f e i n C a m b r i d g e

C am bridge, was, since V ienna, the first place w here he could stay for m ore than five years, and apart from C openhagen the longest stay anyw here was th ree years. So C am bridge becam e really the first place for h im to settle, and he lived there for 32 years. In C am bridge professors are no t autom atically college fellows, b u t have to be elected. F risch was elected by T rin ity College. H e recalls (B5, p. 203) how a ra the r frivolous response to a request for a curriculum iad helped tow ards tha tdecision. U nfo rtunate ly no copy of th is docum ent seems to have survived.

H e was popu lar w ith everybody in the College as well as in the L aboratory , and he was on very friendly term s' w ith m any, no t only those in w hose com pany he m ade, and enjoyed, m usic. B ut in spite of his cheerful friendliness he was ra ther reserved, and it is difficult to find




people w ho, in those early C am bridge days, felt they had really com e close to him .

In 1948 his paren ts cam e to live in C am bridge. H is fa ther had been taken to a concen tra tion cam p in A ustria in 1938, b u t was released w hen offered a post in a p ub lish ing house in S tockholm and perm ission to en ter Sw eden. H is paren ts stayed in S tockholm d u ring the w ar, and m oved to C am bridge on his fa th e r’s re tirem en t, b u t his fa ther d ied shortly afterw ards. H is m o th er d ied tw o years later. O tto R obert had been an affectionate son, w hom circum stances had kep t from contact w ith his paren ts for m any years, and he enjoyed th e ir com pany at least for the short tim e they had left.

H e had a great sense of fam ily, and was said to have an aun t in every tow n. Indeed it was a frequen t experience of his friends to tell h im about a fo rthcom ing trip to som e ou t-o f-the-w ay place, perhaps in South A m erica, and get the response ‘If you have tim e, call on m y aun t th e re .’

T h e m ost d is tingu ished aun t, L ise M eitner, cam e to live in C am bridge w hen, at the age of e ighty-one, she re tired from her research w ork in S tockholm , and R obert could, once again, share w ith her his though ts about physics, un til, near the age of n inety , her s treng th began to fail.

B ut by then he had becom e a fam ily m an in ano ther sense. H e m arried in 1951 U rsu la (U lla) Blau, an artist, a V iennese like him self, and a charm ing person w ho shared his love for m usic and m any o ther of his attitudes; she in troduced h im to the visual arts, for w hich he had no t previously had m uch appreciation, in spite of his fa th e r’s exam ple, and th ro u g h her he w idened his circle of friends beyond the laboratory , the college and m usic. T h ey had a daugh ter and a son, w ho has also becom e a physicist.

T h ey w ere a happy family. T h ere is an am using story about the house in w hich they settled w hen the ir first, ren ted house ceased to be available: O n a Sunday walk in the ne ighbourhood they saw a house w hich they all agreed was the k ind of house th a t w ould suit them . So F risch rang the door bell and asked the lady w ho cam e to the door w hether by any chance they w ere th ink ing of selling th e ir house. I t tu rn ed ou t they w ere th ink ing about it, b u t had no t yet taken any steps to p u t it on the m arket, and before long the F risch fam ily was installed in the house.

H e rem ained active and enjoyed life un til the accidental fall w hich caused his death after a short period in hospital. H e ju s t m issed his seventy-fifth b irthday , to w hich he had been looking forw ard.

I t is hard to do justice, in a b rie f m em oir, to the charm of his personality , b u t fortunately he was able to com plete his au tobiography (B5) w hich can make up for th is inadequacy.

In the w riting of th is m em oir I have been assisted by inform ation or com m ents from M rs L . A rnold , P rofessor E. H . Bellamy, S ir R obert C ockburn , P rofessor G . W . H utch inson , D r A. J. Oxley, S ir Brian




P ippard , M r G . G . Scarro tt, P rofessor K. F. Sm ith , M r P. W oodford, Sir D enys W ilkinson and particu larly M rs U lla Frisch.

T h e pho tograph is by the late L o tte M eitner-G raf.

References

Bohr, N . & W heeler, J. A., 1939 Phys. Rev. 55, 426-450.W ilkinson, D . H ., 1950 Ion chambers and counters, p. 144. Cambridge University Press.

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(2) 1928

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1931

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1933

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19341935

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42-48.Induced radioactivity o f sodium and phosphorus. N ature, Lond. 133, 721-722.Eine W ilsonkammer m it verlangerter Dauer des iibersattigten Zustandes. Naturwissen

schaften 23, 166—167.Induced radioactivity o f fluorine and calcium. N ature, Lond. 136, 220.(W ith E. T . S0RENSEN) Velocity of ‘slow neutrons’. N ature, Lond. 136, 258.(W ith G. Hevesy & H. C. A. M cKay) Selective absorption of neutrons by gold.

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Selective capture o f slow neutrons. M ath .-fys. M eddr 14, no. 12.(W ith H. v. H alban & J. Koch) T he slowing-down and capture of neutrons in

hydrogenous substances. M ath .-fys. M eddr 15, no. 10.(W ith H. v. Halban & J. Koch) Experim ents on the magnetic properties of free

neutrons. Phys. R ev. 53, 719—726.(W ith L ise M eitner) Disintegration of uranium by neutrons; a new type of nuclear

reaction. N ature, Lond. 143, 239-240.Physical evidence for the division of heavy nuclei under neutron bombardment.

N ature, Lond. 143, 276.(W ith L ise M eitner) Products of the fission of the uranium nucleus. Nature, Lond.

143, 471-472.(W ith L ise M eitner) Products of the fission of uranium and thorium under neutron

bombardment. M ath .-fys. M eddr 17, no. 5.Statistical calculation of com posite decay curves. Nature, Lond. 143, 852-853.(W ith R. Peierls) Radioactivity and sub-atom ic phenomena. A . Rep. chem. Soc. 36,

7-32.Radioactivity and sub-atom ic phenomena. A . Rep. chem. Soc. 37, 7—22.(W ith R. Peierls) On the construction of a ‘super-bomb* based on a nuclear chain

reaction in uranium. Part I reproduced in Margaret Gowing, Britain and atomic energy 1939-45 , M acmillan, 1964, pp. 383-395; Part II reproduced in R. W. Clark, L izard, M ethuen, 1965, pp. 215-217.

Radioactivity and sub-atom ic phenomena. A . Rep. Chem. Soc. 38, 287—297.Isotope analysis of uranium samples by means of a-ray groups. Liverpool T ube Alloys

Report.Absolute calibration pf a neutron source. Liverpool T ube Alloys Report.Radioactivity and sub-atom ic phenomena. A . Rep. Chem. Soc. 40, 5—11.Statistics of m ultiplicative processes. A .E .R .E . reportScintillation counters. H elv. phys. A cta 23, suppl. 3, 150.(With S. G. F. Frank & G. G. Scarrott) A mechanical kick-sorter (pulse-analyser).

Phil. M ag. 42, 603-611.(W ith D . J. L ittler) Pile m odulation and statistical fluctuation in piles. Phil. M ag. 45,

126-140.La radioactivite artificielle et la physique.^ . Phys. Radium, Paris 16, 748—753. (Lecture

at the celebration of the 25th anniversary of the discovery of artificial radioactivity).(W ith D . N . Olsen) Detection of coherent bremsstrahlung from crystals. Phys. Rev.

L ett. 3, 141-142.Betrachtungen fiber koharente Bremsstrahlung. acta phys. austriaca 12, 331-335.M olecular beams. Contemp. Phys. 1, 3-16.Parity non-conservation in weak interactions. Prog. nucl. Phys. 6, 267-273.(With A. J. Oxley) A semi-automatic analyser for bubble-chamber photographs. Nucl.

Instrum. M eth. 9, 92—98.T im e and relativity. Contemp. Phys. 3, 16-27.N uclei and nuclear reactions. Contemp. Phys. 6, 81-93.Take a photon . . . Contemp. Phys. 7, 45—53.(W ith J. D avies & B. S. B. Street) Sweepnik, a fast semi-automatic track-measuring

machine. Nucl. Instrum. M eth. 82, 54-60,T he conceptual problems of quantum theory from the experimentalist’s point o f view.

In: Quantum theory and beyond (ed. T . Bastin), pp. 13-21. Cambridge University Press.

Measuring bubble-chamber tracks. (Conference on Machine Perception.) Inst, of Physics Conf. series no. 13.

Presenting physics. Physics Bull. 25, 392.

General Essays, Popular Articles, Historical (G l) 1946 T he tools of nuclear physics. Penguin Science News 2, 128-161.



304

(G 2) 1947(G 3) 1948(G 4) 1950(G 5) 1951

(G 6) 1953(G 7)(G 8) 1954(G 9)(G 10)( G i l )(G 12)(G 13)(G 14)(G 15)(G 16) 1955(G 17)(G 18)(G 19) 1956(G 20)(G 21)(G 22)(G 23)(G 24) 1957(G 25)(G 26)(G 27)

(G 28)(G 29) 1959(G 30)(G 31)(G 32)(G 33)(G 34)(G 35) 1960

(G 36)

(G 37)(G 38)(G 39)(G 40)(G 41)

(G 42) 1961(G 43) 1962(G 44) 1963(G 45)(G 46) 1964(G 47)(G 48) 1965(G 49)(G 50) 1966(51)(G 52) 1967(G 53)(G 54)(G 55) 1968(G 56) 1970

Lectures on nuclear physics at A .E .R .E .M eson theory and radar. Technion Yb.T he cyclotron and its lim itations. Discovery 11, 262—266.T he artificial acceleration of atomic particles. Proc. R . Instn G t. Br. M ay 11; N ature,

Lond. 168, 849-851.Causality in m odern physics. The Listener 49, 138—142.Giant accelerators; what do we expect o f them? Times Sci. R ev. Sum m er, p. 2. Individuality in m odern physics. The Listener 51, 57—58.H ow atomic energy works. The Sunday Times 6 October.Atom ic weapons. N ature, Lond. 173, 477.Atom ic energy; how it all began. B r. J . appl. Phys. 5, 81—84.Scientists and the hydrogen bomb. The Listener 51, 556.H ow the hydrogen bom b works. The Listener 51, 907—908.Atom ic weapons. Atom . Scient. J . 8, 193.Atom ic weapons. In: Atom ic energy, a survey. London: Taylor & Francis.Counting atomic particles. Times Sci. R ev. Spring, p. 6.H igh-energy accelerators. T he synchrotron. Discovery 16, 450.T h e anti-proton. Discovery 51, 498.On the feasibility o f coal-driven power stations. Nucl. Engng, Lond. pp. 268-269. T he anti-proton. Nucl. Pw r 1, 51-52.T he discovery o f the anti-proton. The Listener 55, 16—17.Letter to a young scientist. The Listener 56, 269, 350.Anti-particles and anti-matter. Times Sci. R ev. W inter, p. 1.T he quest for anti-matter. N ew Scient. 1, 31 January 37-39.H ow nuclear fission came to be discovered. N ew Scient. 2, 29—31.Parity is not conserved. Univ. Q uarterly 11, 235—244.D ie Probleme der Energieerzeugung aus W asserstoff. Osterreichische Studiengesell-

schaft fur Atom energie Ges. m .b .H . (SG A E ).Peaceful uses o f atomic fission. A tlan tic M on.T he energetic nucleus. United Nations News January—M arch, pp. 7—10.T he new particles. Bull. Inst. P hys., Lond. 10, 137—142.Probing the atomic nucleus. N ew Scient. 6, 228—230, 416.T his age of m agnetism . The Listener 61, 1108—1109.M easuring atoms. The Listener 62, 1161—1163.T he new elementary particles. Times Sci. R ev. Autum n, p. 12.Are the laws of nature symmetrical? Proc. R . Instn G t Br. 38, 249; N ature, Lond. 187,

638-647.(W ith S ir J. Cockcroft & I. G. John) Nuclear energy: its nature, control and use.

U N A Peacefinder pam phlet, no. 29.Fundamental particles. In: Science S u rvey , pp. 9—22. Vista Books.Exploring the sub-atom ic world. The Listener 63, 119—120.T he strange particles. The Listener 63, 173—176.Strangeness and parity. The Listener 63, 217-218.Introduction to: N iels Bohr’s Atomic theory and the description of nature. Cambridge

U niversity Press.T he elementary particles. Discovery 22, 515—524.Observation and the quantum. March 1962, p. 309.M eans of observing fundamental particles. Penguin Science Survey.T he m agnetic proton. The Listener 70, 459—460.T he new fundamental particles. The Listener 71, 119—120, 173, 176, 217—218. Causality. The Listener 72, 83—84.Poor m an’s S .M .P . Trans. Nucl. Sci. I.E .E . 12, 196-198.M olecular beams. Scient. Am . 212, M ay, pp. 58—74.T he particles o f modern physics. Proc. Instn elect. Engrs 113, 529—537.Sym m etry laws in dispute. The Listener 76, 725.(W ith J. A. W heeler) T he discovery of fission. Physics today 20, 43-52.W hat is physics? B .B .C . Publications.Tracks galore. Camb. Res. 2, 3.(W ith J. A. W heeler) D iscovery and m echanism of fission. Physics Bull. 19, 13—20. T he first nuclear explosion. N ew Scient. 47, 274-278.

Biographical Memoirs



(GS7)

(G 58)

(GS9)(G 60)(G 61)(G 62)

(G 63)(G 64)

(G 65)(G 66)(G 67)

(G 68)

(B l)(B2)(B3)(B4)(B5)

(E l)

(E2)(E3)

(R l)(R2)(R3)(R4)

(R5)(R6)(R7)(R8)(R9)(RIO)( R l l )(R12)(R13)(R14)(R15)

(R16)(R17)

1974 D istinguishing the main types o f radioactivity. Cassette tape recording, Spring GreenM ultim atic, W ashington, D .C .

T he origin o f nuclear forces. Cassette tape recording, Spring Green M ultim atic, W ashington, D .C .

‘Som ebody turned the sun on with a sw itch’. Bull. A tom . Sci. April, pp. 13-18.1975 A walk in the snow. N ew Sclent. 60, 833.

Shooting sparrows in the dark. N ew Sclent. 65, 654-657.1977 Early steps towards the chain reaction. In: R udolf Peier Is and theoretical physics (ed. I.

J. R. A itchison & J. E. Paton). pp. 18—24. Pergamon Press.T he first sub-atom ic particle. N ew Sclent. 76, 408-410.‘W hy’. In: Encyclopaedia of ignorance (ed. R. Duncan & M . W eston-Sm ith), pp. 1-4.

t*ergamon Press.1978 Im possible things. N ew Scient. 78, 688-689.1979 T he life and tim e of Albert Einstein. N ew Scient. 81, 753-755.

Experim ental work w ith nuclei. In: Nuclear physics in retrospect (ed. R. H . Stuewer), pp. 65-73. U niversity o f M innesota Press.

You can prove anything w ith statistics. In: Lying truths (ed. R. Duncan & M. W eston-Sm ith), pp. 171-179. Pergamon Press.


Books1947 M eet the atoms. A popular guide to modern physics. N ew York: A. A. W ynn.1961 Atom ic physics today. N ew York: Basic Books; Edinburgh: Oliver & Boyd. 1962. 1965 Working with atoms. Leicester: Brockhampton Press.1973 The nature of m atter. London: T ham es & H udson.1979 W hat little I remember. Cambridge U niversity Press.

Books edited1950 Progress in nuclear physics, vol. 1. London: Butterworth-Springer; vols 2 -9 , Oxford:

Pergamon, 1953—60.1958 The nuclear handbook. London: Newnes.1959 Beitrage zur Physik und Chem ie des 20. Jahrhunderts (Lise M eitner, Otto Hahn, und

M ax v. Laue zum 80. Geburtstag) (ed. O. R. Frisch, F. A. Paneth, F. Laves & P. Rosbaud). Braunschweig: Vieweg. Also published as Trends in modern physics. N ew York: Interscience.

Book Reviews1950 Acceleration o f particles to high energies. (Inst, o f Phys). Discovery 11, 340.1951 N ew Atom s (O. Hahn). N ature, Lond. 168, 67.

1955 Atom s in the family (Laura Fermi). N ature, Lond. 176, 850.1957 Nuclear explosions and their effects. (Indian M inistry of Information & Broadcasting.)

N ature, Lond. 179, 799.1959 Cerenkov radiation and its application (C. V. Jelley). New Scient. 5, 1034.

Turning points in physics (Oxford lectures). New Scient. 6, 527-528.1961 From dualism to unity in physics (A. Lande). Contemp. Phys. 2, 323.1960 T he great decision (M . Amrine). N ew Scient. 7, 1555-1556.1961 T he birth of the bom b (Robin Clark). Discovery 22, 318.1962 T he new world (R. G. H ew lett & O. E. Anderson). New Scient. 15, 46.

T he philosophical impact o f contemporary physics (M . Capek). Discovery 23, 44.1963 Physics in the sixties (ed. S. K. Runcorn). Discovery 24, 50.1964 Introduction to the theory of relativity (A. V. Rosser) Contemp. Phys. 6, 155-156.

T he nature of matter (Yuan).1967 N iels Bohr, his life and work (ed. S. Rozental); N iels Bohr (Ruth M oore). Scient. Am.

216, 145-148.1969 Einstein’s vision (J. A. W heeler). Camb. Res. 5, no. 3, p. 75.1977 From quarks to quasars (E. Thom as). N ew Scient. 74, 481-482.




( 0 1 )(0 2 )(0 3 )(0 4 )

Obituaries1955 E. Ferm i. N ature, Lond. 175, 18—19.1970 Lise M eitner. Biogr. M em. Fellows R . Soc. Lond. 16, 405—420. 1975 G. P. T hom son. Phil. M ag. 32, no. 6.1979 L. Kowarski. N ature, Lond. 282, 541.

Note: Frisch’s notebooks, correspondence and other material are currently being catalogued by the Contem porary Scientific Archives Centre for deposit in the library of T rinity College, Cambridge.



otto robert frisch, 1 october 1904 - 22 september...

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