Structure of Potassium and Calcium isotopes studied by

Structure of Potassium and Calcium isotopes studied by Collinear Laser Spectroscopy Gerda Neyens ISOLDE WORKSHOP 2014

Collinear laser spectroscopy Motivation to study K and Ca region Selected results for K isotopes Selected results for Ca isotopes Conclusions and outlook

Collinear laser spectroscopy at CRIS at COLLAPS atomic excited state Hyperfine splitting (100 MHz) detect a resonantly excited ion continuum λ 2 second step laser photon (e. V – 108 MHz) atomic ground state detect fluorescence photons excited state laser photon - low background • bunched beams • new detection system - high resolution (~ 50 MHz) - need about 10. 000 ions/s from ISOLDE - atoms or ions λ 1 Hyperfine splitting Atomic ground state - very low background - high resolution (~ 30 MHz) (see poster 36 by R. De Groote) - need about 100 ions/s from ISOLDE - atoms (and ions)

Collinear laser spectroscopy Measure in a model-independent way 4 properties of an exotic isotope/isomer: - the nuclear spin I - the magnetic dipole moment m - the electric quadrupole moment Q (if electronic and nuclear spin J, I>1/2) - the isotope shift nuclear charge radius by resonant excitation of hyperfine transitions in an atom or ion. J. Papuga et al. , PRL 110, 172503 (2013)

Motivation: p-n interaction beyond N=28 p-n interaction in N=Z Stable isotopes Experiment Z = 20 39 40 41 42 43 44 45 46 47 48 49 50 51 52 Ca Z = 19 38 39 40 41 42 43 44 45 46 47 48 49 50 51 K N=Z N = 20 Proton orbits N = 28 40 1 f 5/2 2 p 1/2 2 p 3/2 28 40 32 28 1 f 7/2 20 1 d 3/2 2 s 1/2 20 N = 32 Neutron orbits

K-isotopes: sensitive to the evolution of proton orbits Excitation energy [ke. V] 2753 2788 2522 1/2+ 980 975 855 715 561 672 474 334 345 NR U 3/2+ Exp. NR U 39 K Exp. NR 41 K I = 3/2 U Exp. NR U Exp. 45 K 43 K Otsuka et al. , PRL 87, 2001, 082502 Otsuka et al. , PRL 95, 2005, attractive 232502 interaction 2 p 3/2 1 f 7/2 20 20 1 d 3/2 2 s 1/2 strong between p 1 d 3/2 and n 1 f 7/2 gap between pd 3/2 and ps 1/2 decreases

K-isotopes: sensitive to the evolution of proton orbits Excitation energy [ke. V] 2753 2788 2522 1/2+ I=1/2 becomes g. s. in 980 47 K What if n 2 p 3/2 gets filled ? ? 975 855 715 561 672 474 334 345 360 466 312 320 3/2+ Exp. NR 39 K 74 ? U Exp. NR 41 K U Exp. NR U 43 K Exp. NR 45 K U Exp. NR U 47 K Exp. NR 78 U 49 K ? 81 Exp. NR U 51 K 2 p 3/2 1 f 7/2 1 d 3/2 2 s 1/2 I = 1/2 interaction strongest between 2 s 1/2 and 2 p 3/2 Touchard et al. , PLB 108 (1982) 169

Ca-isotopes: sensitive to the neutron orbits, are N=32 and N=34 magic ? Nature 498 (2013) 347 Nature 502 (2013) 207 Energy of 2+ state in even Ca establishes magicity at N=32 and N=34 mass measurements up to N=34 establish magicity at N=32

RESULTS Ip=1 - Ip=7/2 - Ip=1/2+ Ip=3/2 - Ip=0 - Ip=3/2+ K. Kreim et al. , PLB 731, 97 (2014) R. F. Garcia Ruiz et al. , submitted to PRC

Magnetic moments and g-factors of odd K 47, 49 K dominated by hole in s 1/2 orbit 49 K wave function strongly mixed with d 3/2 Calculations: SDPF-MU, Utsuno et al. , PRC 86 (2012) SDPF-NR and SDPF-U, Nowacki, Poves, PRC 79(2009) sd for protons pf for neutrons J. Papuga et al. , PRL 110, 172503 (2013)

Occupation of ps 1/2 and pd 3/2 as function of N 1 d 3/2 20 1 f 7/2 28 Only at N=28 and N=30 inversion of proton level occupations 2 p 3/2 1 d 3/2 fully occupied 1 d 3/2 hole in d 3/2 (normal) 2 s 1/2 hole in s 1/2 (inverted) J. Papuga et al. , PRC 90, 034321 (2014)

Evolution of proton s 1/2 -d 3/2 gap through DE(1/2+-3/2+) N Model-independent determination of g. s spin of 49 K = ½+, 51 K = 3/2+ Ab initio (Gorkov-Green`s function) V. Somà, T. Duguet and C. Barbieri to be measured ! Shell model with effective interactions J. Papuga et al. , PRC 90, 034321 (2014)

Isomer shift of 38 g, m. K: effect of p-n correlations at N=Z 1 f 7/2 20 20 1 d 3/2 Ip=0+ 38 Km Ip=3+ 38 Kg increased radius due to 1 p-1 h p and n excitations in the 0+ state 2 s 1/2 Neutron 38 Kg 38 Km charge radius relative to 38 Kg Proton Frequency relative to centroid of 38 Kg (MHz) M. L. Bissell et al. , PRL 113 (2014) 052502 0+ 3+

Root mean square charge radii from Z=18 to Z=26 Fe Mn charge radii relative to N=28 Cr Ti Ca Sc K Ar strong Z-dependence below N=28 little Z-dependence above N=28 no signature of ‘magicity’ at N=32 K. Kreim et al. , PLB 731, 97 (2014)

Spin determination of 51 Ca: I=3/2 From the constant ratio of hyperfine parameters: A(S 1/2) / A(P 3/2) = const. only for I=3/2 the ratio fits correctly for 49 Ca and 51 Ca 2 p 3/2 1 f 7/2 I=3/2 photon counts 51 Ca, R. F. Garcia Ruiz et al. , submitted to PRC frequency (MHz)

g-factor of odd-A Ca: sensitive to odd neutron 39 Ca Effective single-particle g factor 20 R. F. Garcia Ruiz et al. , submitted to PRC 2 p 3/2 1 f 7/2 1 d 3/2 2 s 1/2 20

g-factor of odd-A Ca: sensitive to odd neutron 41 Ca ------ 47 Ca Effective single-particle g factor 20 R. F. Garcia Ruiz et al. , submitted to PRC 2 p 3/2 1 f 7/2 1 d 3/2 2 s 1/2 20

g-factor of odd-A Ca: sensitive to odd neutron 49 Ca 51 Ca Effective single-particle g factor 20 51 Ca 2 p 1/2 2 p 3/2 1 f 7/2 1 d 3/2 2 s 1/2 mixing with configurations from higher n(pf) orbits R. F. Garcia Ruiz et al. , submitted to PRC 20

Magnetic moments of odd-Ca: probing the wave function and testing nuclear theories. All theories fail below N=25 (need excitations across N, Z=20) good reproduction for 47, 49, 51 Ca larger mixing in 51 Ca wave function with NN+3 N calculations Quadrupole moments of odd-Ca: follow seniority scheme when filling f 7/2 and p 3/2 orbits confirms dominant single particle behavior R. F. Garcia Ruiz et al. , submitted to PRC

Charge radii of Ca isotopes no signature for shell closure at N=32 ? to be published

Conclusions and outlook • K isotopes: • magnetic moments, spins and charge radii measured up to N=32 • no Q-moments (small) • re-inversion (back to normal) of proton levels beyond N=30 • enhanced p-n correlations at N=Z • Ca isotopes: • magnetic moments, spins and radii measured up to N=32 • Q-moments of all odd-even isotopes up to N=31 • g-factors reveal less magicity at N=32 than at N=28 • Q-moments reveal dominant single-particle behavior • radii do not show evidence for magic N=32 extend measurements to N=34 ! • recent results on Mn isotopes: see poster 34 by H. Heylen

J. Papuga, R. Garcia Ruiz, H. Heylen, W. Gins, M. Bissell, G. Neyens K. Kreim, K. Blaum, R. Neugart R. Sanchez, C. Geppert, L. Grob, N. Frommen, W. Nörtershäuser D. Yordanov, M. Kowalska Thank you for your attention!

Setup – Ion beam ISOLDE (Isotope Separator On-Line DEvice) Surface Ion Source HRS (High Resolution Separation) (1. 4 Ge. V)