liam vormawah university of liverpool. collinear laser spectroscopy at igisol iv hyperfine...
TRANSCRIPT
Collinear laser spectroscopy of
42g,mScLiam Vormawah
University of Liverpool
Collinear laser spectroscopy at IGISOL IV Hyperfine structure, isotope shift and
nuclear properties obtained Spectroscopy of 42g,mSc Results, conclusions and future work
Contents
Collinear laser spectroscopy
Excited state
Ground state
Photon from laser
Excitation of electron
Electron de-excites; photon emitted
e-
e-
Laser beam
Ion beam
Photon emitted from ion
Hyperfine structure and isotope shift
z
y
x
z
y
x
z
y
x
2Q
202
B
212 ,RRr
1R
2R
Hyperfine structure◦ Fine structure J-states
split and perturbed◦ Splitting due to
magnetic dipole moment, m
◦ Perturbation due to electric quadrupole moment, Q
◦ Angular momentum coupling analogous
◦ (FS)◦ (HFS)
Hyperfine structure and isotope shift
SLJ JIF
'2'
'
' AAAA rFAA
AAM
Isotope shift, dnA,A’
◦ Difference in centroid of HFS between two isotopes
◦ Two components – mass shift and field shift
◦ Change in mean-square charge radius, d<r 2>, obtained from field shift
◦ Transition-dependent atomic factors F and M must be correct!
IGISOL IV – Ion Guide Isotope Separator On-Line; 4th incarnation
Located at University of Jyväskylä, Finland
Setup at JYFL IGISOL
The IGISOL IV Laboratory
Cooler
IGISOL ion guide(Gas cell with thin-foil target)
55o dipole analyser magnet
Beam switchyard
Ion beam to laser setup
JYFLTRAP*
Cyclotron beam line
(from K-30 or K-130)
*Not actually part of laser spectroscopy setup
The RFQ cooler-buncher
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Endplate potential
Z(Cooler axis)
200ms
20μs
Photomultiplier tube
Ion bunchLaserbeam
Doppler tuning electrodes
Ion accumulation
Ion release
Reduces energy spread of ions…◦ 2-d ion trap filled
with He gas◦ Ions cooled to
less than 1eV◦ Reaccelerated to
virtually the same energy
…and also photon background!◦ Ions accumulated
and released periodically
◦ Only count photons when ion bunch and PMT are in alignment
42Sc structure
28
20
p n
28
20
1d5/2
2s1/2
1d3/2
1f7/2
2p3/2
1f5/2
2p1/2
38K structure
28
20
p n
28
20
1d5/2
2s1/2
1d3/2
1f7/2
2p3/2
1f5/2
2p1/2
42Sc – self-conjugate nucleus; i.e. N=Z◦ Doubly-magic 40Ca core plus
two valence nucleons (1p+1n)
◦ I=0 ground state
◦ I=7 isomer
Larger radius expected for I=0 state
38K previously studied by Bissell et al. (2014)◦ 40Ca core minus (1p+1n)◦ I=3 ground state
◦ I=0 isomer
◦ Isomer larger than ground state◦ Expect the opposite in 42Sc…
Spectroscopy of 42g,mSc
K38
19 19
Ca40
20 20
Sc42
21 21
Line of N=Z
42Sc produced using 40Ca(a,pn)42Sc reaction ◦ 30MeV a beam◦ Natural calcium target
Spectra taken on 363.1nm 3d4s 3D2 → 3d4p 3F3 transition◦ Ground and metastable states
present in 42Sc spectra◦ J=2 → J=3 transition occurs in
singly-charged (Sc+) ion◦ Transition from naturally-
populated metastable state – optical pumping showed no improvement
Experimental methodology
42Sc
Results as predicted!◦ 42Sc ground state (I=0) larger than isomer (I=7)◦ Results consistent with those of Avgoulea et al.
(2010) Theoretical input for comparison
◦ Shell model calculations of moments and charge radii
Further investigations along the N=Z line◦ Isomers in other self-conjugates – e.g. 26Al…
Conclusions and future work
Collaborators
University of LiverpoolL. J. Vormawah, B. Cheal, C. Wraith
University of ManchesterP. Campbell, A. Dicker, S. Kelly
KU LeuvenS. Geldhof, G. Neyens, H. Heylen
University of JyväskyläA. Jokinen, I. D. Moore, A. Voss, M. Reponen
Thanks for listening!Any questions?