00OFFICE OF NAVAL RESEARCH

o END-OF-THE-YEAR-REPORT

iPUBLICATIONS/PATENTS/PRESENTATIONS/HONORS/STUDENTS REPORT

for

Contract No. N00014-86-K-0501

Synthesis and Characterization of Mixed Semiconductor-Transition

Metal Clusters

Mark A. Johnson

Yale University

P.O. box 1504A Yale Station

New Haven, Connecticut 06520

Reproduction in whole, or in part, is permitted for any purpose

of the United States Government.

This document has been approved for public release and sale:its distribution is unlimited.

DTICE6 -7LECTE

SJUN 27 1989 L

89 ' " 093

Johnson, Mark A.

PART I

A. Papers Submitted to Refereed Journals (and not yet published).

1. "On the Origin of the Competition Between Photodetachment andPhotofragmentation in the Hydrated Electron Clusters, (H2O,-" Lynmarie A.Posey, Paul J. Campagnola, Mark A. Johnson, Gang-Ho Lee, and Kit H. Bowen,J. Chem. Phys. June 1989 [NSF,ONR]

2. "A Pulsed, High Resolution Photofragmentation Spectrometer for Mass-SelectedCluster Ions," M. J. DeLuca and Mark A. Johnson, in preparation for Rev. Sci.

Instr.

3. "A Simple Electron Acceleration/Deleration Lens for Time-of-FlightPhotoelectron Spectroscopy of Mass-Selected Negative Ions," C.-C. HanY.-F. Yen and M. A. Johnson, in preparation for Rev. Scl. Instr. June,

1989 [ONR]

4. "On the Photoabsorption of Negative Cluster Ions Near th-! Electron DetachmentThreshold: A Study of the (O2)n," Chau-Chung Han, Michael J. DeLuca, andMark A. Johnson, in preparation for J. Chem. Phys.

B. Papers Published in Refereed Journals

5. Michael J. DeLuca and Mark A. Johnson, "Photofragmentation of C,"45s20: Loss of C3," Chem. Phys. Letters 152, 67 (1988)[ONR,PYI].

6. Reactions of Hydrated Electron Clusters (H20)n-: Scavenging the ExcessElectron," Lynimarie A. Posey, Michael J. DeLuca, Paul J. Campagnola andMark A. Johnson, J. Phys. Chem. 93 [NSF]

9. Sections Published

7. M. A. Johnson atd V. C. Lineberger, "Pulsed Methods for Cluster IonSpectroscopy," in Techniques of Chemistry, Vol. XX, Techniques for the StudyIon Molecule Reactions, Edited by J. M. Farrar and W. H. Saunders, John Wiley& Sons, 1988). P. 591.

E. Technical Reports

8. "A Simple Electron Acceleration/Deceleration Lens for Time-of-flightphotoelectron spectroscopy of mass-selected negative ions," C.-C. Han,Y.-F. Yen, and Mark A. Johnson, Report #6.

9. "A Pulsed, High Resolution Spectrometer for Mass Selected Ions," Michael J.DeLuca and Mark A. Johnson, Report #7.

10. "Wavelength Dependent Photofragmentation of Hydrated Electron Clusters,(H20),-: A Half-Collision View of the Zero Energy Electron CaptureResonance," Paul J. Campagnola, Lynmarie A. Posey, Mark A. Johnson,Report #8 [NSF].

H. Invited Talks

ll."Electron transfer reactions of the hydrated electron clusters:MIcro-calorimetry in a molecular beam," Dynamics of Molecular Collisions,Asilomar, CA. July 1989 [NSF].

12."Cluster ions in reaction dynamics: Isolation and selective excitation ofreaction intermediates," Spectroscopy of Free Radicals, Dalian, China,September, 1989 [NSF].

13."Cluster analogues of the hydrated electron: Spectroscopy, Photochemistryand reactivity," Cluster symposium at Pacifichem '89, Hawaii, December,1989 [NSF].

14."Electron transfer reactions of the excess electron in (H2O)n - clusters:molecular beam micro-calorimetry," Cluster symposium held at the ACSnational meeting at Miami, Sept. 10-15, 1989.

I. Contributed Presentations at Topical or Scientific Conferences

15. "Photochemistry of Hydrated Electron Clusters, (H20),- (155n<40),"L.A. Posey and M. A. Johnson, Poster at the Fouth InternationalSymposium on Small Particles and Inorganic Clusters, Aix-en-Provence,France, July, 1988.

16. "Photodissociation and Photodetachment of Hydrated Electron Clusters(H20)n-: The Mechanics of the Onset at n-15," L. A. Posey and M. A.Johnson, Talk at the Fourth Internntinno! Tje-.r Science Conference,

17. "Pulsed Methods for Ion Spectroscopy," M. J. DeLuca and M. A. Johnson, posterat the Research Conference on Molecular Electronic Spectroscopy, Iled'Oleron, France, September, 1988.

18. "Trapping of intermediate complexes in ion-molecule reactions: Photoelectronspectroscopy of three isomeric N202 complexes," Lynmarie A. Posey andMark A. Johnson, Poster at the Dynamics of Molecular collisions conferenceAsilomar, CA, July 1989._i5 . I

DTIC TABUnd,II oLnced

04 Yjusti, i .. -

INSPECIWJs'1 ifl__,By .. .. .

sei

m u i I I I II I | I IIa

J. Honors, Awards, and Prizes

Presidential Young Investigator Award, 1987-1992National Science Foundation (Feb. 1987)

Junior Faculty FellowshipYale University (1988-1989)

K. Number of Graduate Students Receiving ONR Support

None.

L. Number of Post docs Receiving ONR Support

One: 100%Dr. Chau-Chung HanPh.D. Stanford University 1987

PART II

Principal Investigator: Mark A. Johnson, Assistant Professor(203 432-5226)

ONR Scientific Officer: Dr. David L. Nelson (202-696-4409)

Project Description: Our primary objectives are to study the

electronic and geometrical structures of mass selected clusterions, with emphasis on clusters containing semiconductors,

metals and mixed compositions. Our early efforts focussed onthe use of ultraviolet photoelectron spectroscopy (UPS) of a

mass selected negative ion beam to provide a low resolution

diagnostic of the electronic band structure. In order todetermine cluster geometries, we are expanding our techniquesto include high resolution laser photofragmentationspectroscopy.

Significant Results in the Past Year:

Technique development:In the past year, we have completed construction of a single-longitudinal mode pulsed dye laser and demonstrated itsperformance on the mass-selected ion beam using NNO+ as atarget ion. This system is sLate-uf-#iith-arL in tczuo of power

and linewidth capabilities, which will be invaluable inunravelling the spectral congestion expected in the cluster

systems. We have also been working on photoelectronspectroscopy on a technical level where we have developed a way

to control the photon-energy resolution problem inherent in the

pulsed PES technique which we developed at Yale.

Cluster Photophysics:We have undertaken a series of experiments to understand whymany cluster Systcm (e.p. Ag,-, Cn-) efficientlyphetodissociate when emcltod .ear their electron detachmentthresholdq. We have looked at the water and oxygen negativeions, where water physically stabilizes the electron in anotherwise closed shell system while oxygen has an open shellstructure similar to metal systems. The water experiment isparticularly enlightening since we were able to show that the

photodissociation propensity is simply related to the excesskinetic energy of the electron after excitation, which was

determined using photoelectron spectroscopy. Thus, intra-cluster electron-phonon scattering appears to mediate the

ability of clusters to capture the excited electron before itleaves the cluster.

Internal energy control:

In yet another "first," we have succeeded in controlling theinternal energy content of (H20)n- clusters by varyingconditions of the expansion. So far we have seen cooling inthe ensemble on the order of one monomer bond energy.

Summary of Plans for next year: Since our contract expires onJuly 1, 1989, we summarize likely future directions for thisresearch. It is now clear that optical excitation ofnegatively charged clusters is quite complex and notunderstood even is very simple systems. A particularlyfruitful direction therefore appears to be a high resolutionstudy of the near threshold region of clusters in the which thecharge is initially localized. An outstanding candidate forthis study is the I -( 0 2)n clusters. Here, we envision twocomplementary experiments to probe the electron scatteringafter excitation where the photofragmentation cross section andthe photoelectron spectra are obtained as a function ofexcitation energy near the I- photodetachment threshold. Aparticularly exciting prospect is the opportunity to directlyobserve scattering into the autodetaching levels of 02 solventmolecules. This type of photon energy-dependent probe can thenbe extended to the case of metals which are characterized by adelocalized electron.

G. STUDENTS AND POSTDOCS

Students:Lynmarie A. PoseyMichael J. DeLucaPaul J. CampagnolaYu-Fong YenDonna Cyr

Post-doc:

Dr. Chau-Chung Han

PART III.

SEE ATTACHED SHEETS

PROBING THE "CONDUCTION BAND" OF CLUSTERS WITH

OPTICAL SPECTROSCOPY

1. THE NEED FOR NEW DIAGNOSTICS

2. DETERMINE THE ELECTRON BINDING ENERGIES USINGPHOTOEMISSION-

SIZE SELECTION USINGNEGATIVE ION PHOTOELECTRON SPECTROSCOPY

3. PHOTOEXCITE THE CLUSTER NEAR THE ELECTRONBINDING ENERGY

4. MONITOR THE BRANCHING BETWEENPHOTODETACHMENT AND PHOTOFRAGMENTATION

5. LOOK FOR SIMPLE MODELS TO RECOVER BEHAVIOR OFBRANCHING RATIO USING ELECTRON-PHONONSCATTERING

~1*- siunooj uoio~ej.oiqcI010cv5

CC

C*%J

c'J)

C

0>

C)

10- :. -... L L

C

C) CD0 C)C

CC; C; C C

S'PaieA wfl1uefl) uo!iBujuwejjo1oLcd

CONCLUSIONS

1. PHOTOEXCITATION OF EXCESS ELECTRON ISCHANNELED INTO ELECTRON KINETIC ENERGY

2. CAPTURE OF THE ELECTRON IS MEDIATED BYINELASTIC SCATTERING SIMILAR TO THAT SEENIN ELECTRON SCATTERING FROM SOLIDS

3. OTHER SYSTEMS STUDIED SO FAR WHICH INDICATEPHOTOEXCITATION OF THE ELECTRON OR HOLEINTO "CONDUCTING" STATES OF THE BULK:

Ar'-Xen

+

S(02) fI- (on)Cn"

4. RELEVANCE TO HETEROGENEOUS SYSTEMS:

EXPLORE CHARGE LOCALIZATION IN .AXED SYSTEMSSUCH AS [0 2 Agnf

PART IIID.

In the design of materials at the atomic and molecular level, we arelead to explore the properties of a collection containing anywhere from a fewto a few hundred atoms, as these clusters may provide the building blocks formaterials with tailored properties. A major challenge facingexperimentalists studying these microscopic systems is that, while orderedsolids can be characterized by many highly developed techniques (LEED, Auger,photoemission, conductivity, optical spectroscopy, etc.) the cluster systemsrequire either entirely new or highly adapted methodologies to define theirbehavior.

We have therefore undertaken the task of developing cluster diagnostics

and have succeeded in demonstrating a gas phase analogue of photoemission,negative ion photoelectron spectroscopy, on cluster systems. The novelty ofthis technique is that clusters with precisely determined compositions canbe systematically studied as a function of size and stoichiometry. We arenow working on methods for probing the nature of the conducting states in theclusters by photoexciting an excess electron and monitoring the propensityof the cluster to capture the outgoing electron before it escapes theclusters. This method couples photoelectron spectroscopy withphotofragmentation spectroscopy to get the best overall view of the excitedstate dynamics.

1n the tigure shown in part IIIC., we show the photoelectron spectrum(dashed line) and photofragmentation quantum yield (points) of the excesselectron attached to water clusters, (H2 0) 25-. The dashed line gives a map ofthe distribution of electron binding energies (taken by Kit Bowen at JohnsHopkins University), while the photofragmentation quantum yield provides ameasure of the propensity of the photoexcited electron to escape. The solidline through the points is derived from a simple theory for the electroncapture process where electrons photoexcited with less than 0.1 eV kineticenergy are captured with unity efficiency. Interestingly, this value of 0.1eV is also the characteristic of the inelastic scattering of electrons offof solid water surfaces.

Futuye directions for this study include mixed metl/insulator systemssuch as oxygen adsorbed onto silver with an excess electron, 02 Agnl]. Herewe investigate the propensity of the system to localize the charge on the 02

moiety and again look for excitation into the conduction band of thematerial, this time presumably into the states associated with the silvercomponent of the clusters. Since the negative ion channel seems to mediatevibrationally inelastic scattering of CO from surfaces, this study can alsoprovide a direct probe of the nature of the adsorbate in the presence of thenegative charge.

OFFICE OF NAVAL RESEARCHCONTRACT #N00014-86-K-0501

TECHNICAL REPORT #6

A Simple Electron Acceleration/Deceleration Lrns for Time-of-FlightPhotoelectron Spectrosocpy of Mass Selected Negative Ions

C.-C. Han, Y.-F. Yen and M. A. Johnson

Department of ChemistryYale University

225 Prospect StreetNew Haven, CT 06511

In preparation for Publication

in

Review of Scientific Intruments

Reproduction in whole or in part is permitted for any purpose of theUnited States Government.

This document has been approved for public release and sale; its distribution isunlimited.

REPORT DOCUMENTATION PAGE_a -- As F : C PEST*CT VE JAAK "ZS

Unclassified2, Si P . .&- ' , CASOO N STNS ,-ONA AA, ..,Tv Zf AEPOM.

This document has been approved for

2bC..OOO.P4GNAONGSC--OUE public release and sale, distribution ofthis document is inlimitpd

A VEMOCU WNG ORGAN-iZAT-ON ANPONT NUM80IS) S. MONOTOiIDWG ONGANaIZATION AIPORT NLJMiAIS)

Technical Report 46%% 0 *OMG OAGAkZATIO b. ICS SYmSOL 7e& NAML 00 WOMNITOIqNG oGANIZAT&O

Yale University Chemistry Procram6C ACOAhSS C,' S(6f .9. ?IP Cdw, 7b. AOCAISS C7,1. $0e e-d ZIP Code'

Department of Chemistry 800 N. Quincy Street225 Prospect Street Arlington, VA 22217NewHaven, CT 06511

soNA ̂ Mao$ P o£N r''SPONSOOUNG Sb OFF ICi SY#ASOL 9. P0CiO c ENhE T NSTP1' k44Nt OENT4,CAT,14 NtMAGER,DNG4&N.2ATON If A& 1 IP I6 j N00014-86-K-0501

S AOORiSS 'C,0 .1iwie e ZIP cod, 10 SOUICI OfF UJNOING NOS

800 N. Quincy Street P-OORNAI POJICT ! WORK WNIT

Arlington, VA 22217 itLE MaNNO. 0 O0 ,40

T T LE acua , C

Characterization of Mixed Clusters12. Ps 0lSONAL AUT"OIISI

Mark A. b -EPOr12& TYPE Of REPORT I:& T M C'vO Vi 601 EO EOT(,V ei 5PGECU

Technical no" '0 ___°___088/7/25

16 SPPLiMEINTAY 14OTATION

17 COSATI COOS IL SwOJS CT TIEAS ICon.> sti., *A e we o w douU.De.,.w ide"Omf4 6d~ 7 blocIRIrS7PI.,, omVou sue GA Cluster ion photoelectron spectroscopy, electron optics,

PES of mass-selected clusters.

It AGGIACT ,C o n4 sawd of ne o ad l f by WOck NamU *'t

Since its introdurtinn in 1986. pulsed photoelectron spectroscopy of mass selected

inn hrm, I; tapily becoming a central tcol in the study of cluster ions, molecular

ions with high electron affin.ties (-:3.5 eV) and even in tle spectroscopy of tne

transition states of neuir:l chemical reactions. A traditional shortcoming of time-

of-flight photoelectron spectroscopy when applied to negative ion beams is that the

resolution, 6E is highly dependent on the electron energy as:5E cc E312 X At

where At is tl-e pulse width of the laser. We present a simple electrostatic lensing

scheme which manipulates the electron kinetic energies in order to access the

highest resolution possible to the spectral region of interest. An unanticipated

b'nefit of this approach is that very low energy electrons can also be collected,

allowing PES to probe the region very close to the electron binding energy.

20 OASTI IUTIONIAVAILAS

I IlITY OP AISTAACT 21 ASSTNACT SICURIy C..ASSiF CATION

UNCLAss,,,EoINLu-,to .SAME AS APT :- TC %S.nS C Unclassified2. NAME OF *ISPONSISIA NOvOAL |22b "E AVMONE tA IN .2c Z09 :1 5'%41C6

!,,c,.aE 4 'W Cod*,Dr. David L. Nelson 202-696-4410

00 FORM 1473, 3 APR eo,'row O. I AAP ,3 Is ossoL i.

19 S.C..I. r..LASSIVCAIOC OP l' RAGS

REPORT DOCUMENTATION PAGE

Unclassified

2SI.'CA15F -CA"'O% ,TORT 3 0 STm.uTON.AoI-6.T :F RE90N

This document has been approved for

2b OC.AS1iCAT-OO*GkAOINdGSCHEOUf Public release and sale, distribution ofthis document is unlimited.

A *f mCRMING OPmGANZAION AFPOVN NUMVE0%ISI S. MONITORING ORGANIZATION REPORT NtJMSS1ItS)

Technical Report #7____________________

%& NMt Of OSAPOPMIt4G ORGANIIIZATIO14 6. OFFICE SYMBOL 7&. NAME OF MONITORING OPIGANIZATION

Yale UnversityChemistry Proga4, AOOXESSc' C.1, .Saei AZP Code, 7b AOOAEjSS CaEy. Sgtt Ad ZIP Code,

Department of Chemistry 800 N. Quincy Street225 Prospect Street Arlington, VA 22217

Ge N4AUG OF FUNOING SPONSORiNG Gb OFFICE SYMBOL 9. PROCUREMENT iNSTR~uMENr IDENTIFICATION NuMGER

ORGANIZATION lop etooi

N00014-86-K-0501fc ALOORISS 'C.y. SIG## and ZIP Co"a' 10 SOURCE OF PUNOING NO0S

800 N. Quincy Street EPORAM PROJECT ?ASK WORK WN(T

Arlington, VA 22217 IEM TN.%o4

1 1 TITLE -Ifte~de, Soe:v Clauseot~on,

Chrceiainof Mixed Clusters _________________

Ma.rk A. Ahnson ____

13& TYPE Of REPORT Ija. TIME COvERIED I&' OA-5 OF REPORT ly, me. 15y V PAGE COU~NT'

Technical IFROMe To 88/7/25IS. SLIPPLEMENTAXY NO0TATIOPY

117 COSAT# Cools 11. SUBJECT 710RM0S IC~anna.. ,&WWu tj'.gewp SOWd ,dimly, by 6400k num~r,

F-ILO GOVu SUB Go High resolution photofragmentation speciroscopy, pulsedtandem time-of-flight, techniques for cluster ion

.r'I Qp-ctrncf-npX19. k ATMACT 'Collignue an vve I pNoeei and ,,ptfV 67 Mbdk mub'

We describe t'L- performance of a pulsed spectrometer whirch r-P-es !OTIS using an:

ionized free jet, mass selects a particular m/e ion tor interacCiion wiith a sir.gJ~e-

rn'-.ie pulsed dye laser, and then analyzes the photofragments with a second mass

spectrometer. of particular interest is the result that the rotational cooling of

the N2 O"* ion achieved in the source can be maintained even after extraction throughthe unskimmed jet. Details of the amplification scheme used in the frequencylocked, single mode, pulsed dye laser are also presented.

20 OiSTRiILTIONAVAILAIL).TV OF ABSTRACT 21 ASSTRIACT SICUAIT -- ASSIF-CATION

LJNCLASSIPOSO'LINLIMITEO , SAME AS APT - 01-C ISERkS - Uncl assi fied22o N4AME OF NESPONSiSLE NOvOi.22b -f-2.-ONE 'luMNIE: :F r :E S 1%40C.

Dr. David L. Nelson 202-696-441

00 FORM 1473, 63 APR I 01eo'N OP I IANt F3 is OSS@LSE.

19 SICL,01I" CLASSIFICATION CP Y..1 PAG~E

OFFICE OF NAVAL RESEARCHCONTRACT #N00014-86-K-0501

TECHNICAL REPORT #8

Wavelength Dependent Photofragmentation of Hydrated Electron

Clusters, (H20).-: A "Half-Collision" View of the Zero Energy

Electron Capture Resonance

L.A. Posey, Paul J. Campagnola, and Mark A. Johnson

Department of Chemistry

Yale University

225 Prospect Street

New Haven, CT 06511

J.G. Eaton, G.H. Lee, and K.H. Bowen

Department of Chemistry

The Johns Hopkins University

Baltimore. MD 21218

Prepared for Publicationin

Journal of Chemical Physics

Reproduction in whole or in part is permitted for any purpose of the

United States Government.

This document has been approved for public release and sale; its distribution is

unlimited.

s-t~

REPORT DOCUMENTATION PAGE.41a o. Uc as.; i-d L F Z % t

o REST0CCT VE W4AAE %-

2. E_ s 1 -A$$,I CAT'ON .- AT 0 .STP1-surON&,A.AA8,.T? Or AEPORT

*-7 This document has been approved for2: O(C.ASSIPCATONdOCOwGAOiNGSCI6OJLI public release and sale, distribution of__________________________________ this document is unlimited.

otCafCAMIFIG ORGANIZATION IIFORT NUMIENISI S. MON4ITORINGO OPIGA4ZATIFW REPORT ftA41RSE(S)

Technical Report #8

4N6MI Of &EFftORMFG ORGANIZATION 0. 0 VICE SYMBOL. U. NAME 00 MONITORINGORGANIZATION

Yale nivesityChemistry Program6c AOOAESS Catl Stage and ZIP Coda. 7b. ADDRESS .C,t),. State &nd ZIP Code.Department of Chemistry 800 N. Quincy Stree

225 rospct SreetArlington, VIA 2217

So NAME Of "i.JNOING.ISPONSORING So. OFFICE SYMBOL 9. PPOCtJAEK4NT INSTRUMENT IDENTIFICATION NLJ064UER

I N00014-86-K-050.Be ADDRESS 'C.,y. Stae Wd ZIP Coda, 10 SOURCE OF FUNDING NOS

800 N. Quincy Street PROGRAM PROJECT? TASK WORK WNIT

Arlington, VA 22217 ELMN O 40 4

I I T IT L E Iftc~aa sacs..r CaaagaaCharacterization ofMixedClusters I_____________________

12. PERSONAL ALIMOIS)M r~k A. Johhnsen

13 YEOFRPR COVEAROM ,'eno 1D ATE OFREPORT IYr. Mo.. Day) IS5 PAGE CCUN(

If. SUPPLEMEN4TARY NO0TATION

17 COSA?. CODIES I& SUjIjCT TERMS lCombno. on mverm i jec*awyen danl &Vmgfb bloe namisbr,

PSI 66 LO Gx,.S GO Threshold photofragmentation of negative cluster ions,I electronic photophysics of cluster ions.19. ASTRACT (Con tinuea n eyvre if wevemfy &"d gdmn bft by &bdCa agmaerI

Photoexcitation of size-selected hydrated electron cluuters, (H20)n-, in the nearIR rr. 'ltz- in- ccm-ct-*tijr ,ctj-.een photofragmentatiori qn. ph-rdetnchment. Toinvestigate the origin of this competition, thne decay probability into ionicfragments for the n-25 cluster was measured as a function of photon energy from0.91 to 3.49 eV. The photofragmentation probability increases rapidly withdecreasing excitation energy in the general vicinity of the vertical electronbinding energy of this clusters (1.3 eV) determined via photoelectron spectroscopy.This result suggests that fragmentation accompanies photoexcitation of the excesselectron with near zero kinetic energy. Thus, photofragmentation appears to proceedthrough an optically prepared intermediate similar to that reached in electronscattering from neutral clusters which displays an enhanced dissociative attachmentpathway with near zero kinetic energy electrons.

20 OISTRPITIONJAVAILAGILTY Of ABSTRACT 21. ABSTRACT SECURITY. C.ASSPCATMOF

LCLASWlI90.UNLIMITEO :2 SAME AS APT ZOTIC VS6S C Unclassified22a NAME OF RESPONSIBLE NOivsOwAL 22b EL.E'.0ONE NUMBER :2c _1F : S %490i.

'I',e.d k've Code,Dr. David L. Nelson 202-696-4410

0O FORM 1473. 83 APR 401vION OP I JAN 73 IS OSOLSlE.

19 SC6JRiTv CLASSIFICATION Of TWIS PAGE

- - - ; ~ -.~N

REPORT DOCUMENTATION PA1GE. - _ a :-Ass F ZA-C- 10 JIGSTrRCT-vF -ARK %,7S

Unclassified2. SEC. - C..ASS,OCAION wrOAT 3 0STRISLuT.OfN,AVA11_A&.LTY (Z) AEPOR7

This document has been approved for2b OIC.ASifCATOOOVft4GAOiPNGSCmEOU&E1 public release and sale, distribution of

this document is unlimited.d.1E17)1114ING OAGANIZAT)OP REPORT NUMBEMIS) S. MONITORING ORGANIZATION REPORT NUMBERItSI

Final Report______________________________*% AMIEO QPECRFORMING ORGANIZATION ow OFFICE SYvMBOL, 7d. NAME Of MONITORING ORGANIZATION

Yale University I_______Chemistry Program6c ADDRESS Cd." Staff and /lP Code, 7b. ADDRESS eC.1y. Siane and ZIP Codet

Department of Chemistry 800 N. Quincy Street225 Prospect Street Arlington, VA 22217

&NAME OF 19NOING S5PONSORING ob. OPPICE SYMBOL 2. PROCUREMENT INSTRUMENT IOENTIPiCATION NUMBER

N00014-86-K-0501st ADDRESS 'C"t). Sial' and ZIP Code, 10 SOURCE Of FUNDING P40S

800 N. Quincy Street PROGRAM PROJECT TASK WORK WPjN1T

Arlington, VA 22217 ELEMENT NO. No. P01

II TITLE -feludif SacuntY Cigesti.,ont

Characterization of Mixed Clusters12. PERSONAL AUTmORIS)

13& TYPE OF REPORT 13b. TIME COVERED 114. DATE OF REPORT 1yr. N~O.. Day) Is PAGE COUNT

Technical FROM ~ o89/6/20

14. SUPPLE MENTARY NOTATION

17 COSATI CODES I&. SUBJECT TERMS fContnae On ,warvi if nleeeuePP and advatify by block number)

FIELD GROUP $sU. G1111

19. AOSYRA CT sConaana,,e on mogm'u of nacqsady and Ida at~ by 6iock nufflberj

S)ce attacha~d sheet

20 DISTRl BUTION/AVAILAOBI.ITY OF ABSTRACT 21 ABSTRACT SECURITY C..ASS'F CATION

UNCILASSIFIEO'UNLIMI TEO IZ SAME AS APT -: OTIC USERS C Unclassified22& NAME Of RESPONSIBLE *NOViOwAL. 22b 'E.E*'ONE NUjMBER :2c :;Fr CE SIM0SC.

'IcIuAE iv7 Cod*,

Dr. David Nelson 202-696-4410

OD FORM 1473, 63 APR EDITION OP I jAw 73 IS OBSOLETE._______________

19 SECURITY CLASSIFICATION oft ?"s* PAGE

OFFICE OF NAVAL RESEARCHCONTRACT #N00014-86-K-0501

TECHNICAL REPORT #7

A Pulsed High Resolution Spectrometer for Mass Selected Ions

M. J. DeLuca and Mark A. Johnson

Department of Chemistry

Yale University

225 Prospect Street

New Haven, CT 06511

In preparation for Publication

in

Review of Scientific Intruments

Reproduction in whole or in part is permitted for any purpose of theUnited States Government.

This document has been approved for public release and sale; its distribution is

unlimited.

In the design of materials, we are often faced with the problem that

a desirable set of electrical or mechanical properties may be associated with

a dissordered or unstable stoichiometry of the system. The long standing

problem of introducing Ohmic contacts onto GaAs is such as example where we

seek a method of tailoring the junction with a partially diffused metal

layer. We immediatly ask the questions:

i. How do we determine the electronic properties of unstable, probablydisordered systems?

2. How do these properties vary as the compositions aresystematically varied?

3. How do we fabricate devices based upon thesemolecular-level building blocks?

In order to pursue the answers to these questions, we have initiated

an avenue of research to explore the properties of atomic and molcular

aggregates which are size selected using mass spectrometry and and then

analyzed using opical and photoelectron spectroscopies [technical report *1].

Thus, arbitrary compositions can be synthesized in a free jet expansion and

interrogated directly in the gas phase. This methodology is sufficiently new

t t an entirely new c'las o± peci-s b-s only rpepnfly hecome amerabic fur

study, creat1i,& a fertile ground for investigating the physical chemistry of

heterogeneous systems at the atomic level [see technical reports #2 and #3].

The specific questions at the focus of our attention are the electronic

structures and physical properties of cluster ions. In order to study the

fundamental aspects of electrical conduction in these microscopic systems,

we have chosen as a test case a system where only one electron is isolated

in a sea of species which are polarizable but which have no available states

in which to propagate the electronic wavefunction. Such a system represents

a kind of hydrogen atom for cluster research. The rare gas ions such as

(Xe),- would appear ideal for such a study; however, they are exceedingly

difficult to prepare. We, therefore, presently content ourselves with the

(H2O)n- system as a prototype. We study this system using angle- and energy-

resolved photoelectron spectroscopy, photofragmentation spectroscopy, and

reaction chemistry [technical report #8]. We have, in fact, pioneered the

development of a new technique, pulsed photoelectron spectroscopy of mass

selected negative ions [technical report #1] to carry out this project.

Thus far in the water system we have determined the nature of the

ground state electron configuration, the scattering events which occur upon

photcexcitation and the competition between evaporation of the electron

(deteachment) and a water monomer (fragmentation). We have extended these

ideas to the carbon dioxide anion system, the rare gas cation systems (Xen+,

Arn+) with one extra hole instead of an electron, and finally, we begin to

extend this work to systems to species with a high ground state degeneracy

which characterizes metals and semiconductors where we have worked on oxygen

Ir -. ! G .... jell as on carbut C L[Chnlca . rercrt #.*4

Technical reports

1. "Demonstration of a pulsed photoelectron spectrometer on mass-selectednegative ions: 0, O2-, and 04"," L. A. Posey, Michael J. DeLuca andMark A. Johnson.

2. "Pulsed photoelectron spectroscopy of negative cluster ions: isolation ofdistinguishable forms of N20-," L. A. Posey and M. A. Johnson.

3. "Photoelectron spectroscopy of (CO2)n- clusters with 2<n<13: cluster sizedependence of the core molecular ion," M. J. DeLuca, B. Niu, and M. A.

Johnson.

4. "Photofragmentation of Cn-: loss of neutral C3," M. J. DeLuca and M. A.Johnson.

5. "Photofragmentation of (0 2)n', n-3,4: Direct determination of the 02-(v)vibrational distribution using pulsed photoelectron spectroscopy," C. -C.Han, Y.-F. Yen and M. A. Johnson.

6. "A Simple Electron Acceleration/Deceleration Lens for Time-of-flight

photoelectron spectroscopy of mass-selected negative ions," C.-C. Han,Y.-F. Yen, and Mark A. Johnson, Report #6.

7. "A Fuhh=., Hign kasult:on Spectrometer for ftass Selected , ..,,DeLuca and Mark A. Johnson, Report #7.

8. "Wavelength Dependent Photofragmentation of Hydrated Electron Clusters,

(H20),-: A Half-Collision View of the Zero Energy Electron CaptureResonance," Paul J. Campagnola, Lynmarie A. Posey, Mark A. Johnson,Report #8 [NSF].

Papers

..'DPmnnqtration of a pulsed photoelectron spectrumeter on mass-selectelnegative ions: 0-, 02-, and 04-," L. A. Posey, Michael J. DeLuca andMark A. Johnson, Chem. Phys. Letters 131, 170 (1986).

2. Michael J. DeLuca, Baohua Niu, and Mark A. Johnson, "PhotoelectronSpectroscopy of (CO2)n- with 2sn 13: Cluster Size Dependence of theCore Molecular Ion," J. Chem. Phys. 5857 (1988) [NSF-PRF].

3. M. A. Johnson and W. C. Lineberger, "Pulsed Methods for Cluster Ion

Spectroscopy," in Techniques of Chemistry, Vol. XX, Techniques for theStudy Ion Molecule Reactions, Edited by J. M. Farrar and W. H. Saunders,John Wiley & Sons, 1988). P. 591.

4. W. C. Lineberger and M. A. Johnson, "Spectroscopy of Ionic Clusters,"Workshop on Molecular and Cluster Beam Science, (National AcademyPress, Washington, D. C., 1988) P. 67.

5. Michael J. DeLuca and Mark A. Johnson, "Photofragmentation of Cn-'45n:520: Loss of C3," Chem. Phys. Letters 152, 67 (1988)[ONR,PYI].

6. "A Simple Electron Acceleration/Deleration Lens for Time-of-FlightPhotoelectron Spectroscopy of Mass-Selected Negative Ions," C.-C. HanY.-F. Yen and M. A. Johnson, in preparation for Rev. Sci. Instr. June,1989 (ONR]

7. "On the Photoabsorption of Negative Cluster Ions Near the ElectronDetachment Threshold: A Study of the (02)n-," Chau-Chung Han, Michael J.DeLuca, and Mark A. Johnson, in preparation for J. Chem. Phys.

8. "On the origin of the competition between photofragmentation andphotodetachment in hydrated electron clusters," L. A. Posey, P. J.Campagnola, M.A. Johnson, G.H. Lee, J. G. Eaton, and K. H. Bowen,submitted to J. Chem. Phys. June, 1989.

Students participating in research:

Lynmarie A. PoseyMichael J. DeLucaP. J. CampagnolaYu-Fong YeLlBaohua NiuDonna Cyr

Postdocs:

Dr. Chau-Chung Han