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?