Collinear laser spectroscopy of scandium and yttrium isotopes at IGISOL IV

This thesis presents the results of two separate collinear laser spectroscopy investigations; one of proton-neutron pairing correlations in the odd-odd self-conjugate nucleus 42Sc, and the other investigating the charge radii of neutron-rich Y isotopes and the sudden onset of nuclear deformation in the Z~40, N~60 region of the nuclear chart. For the first time, the 42g,42mSc isomer shift, and corresponding change in mean-square charge radius, has been studied via collinear laser spectroscopy at IGISOL IV. The result for the change in mean-square charge radius supports the qualitative prediction given by the intuitive picture of proton-neutron pairing, in which the nuclear charge radius should be greater for an I=0, T=1 nuclear state than an I≠0, T=0 state. This result is also, qualitatively speaking at least, in agreement with the results of previous proton-neutron pairing studies, namely studies of the charge radii of 38g,38mK and 50g,50mMn. In addition to this, new values of the atomic factors for the mass and field shift, F and M, have allowed for a recalibration of the Sc charge radii measured previously on the same atomic transition as used here. Spectroscopy has been performed on radioactive Y2+ ions for the first time. The motivation for this was to recalibrate previously measured charge radii for 86-90,92-102Y and isomeric states in 87-90,93,96,98Y, which were measured on the 363.3nm 5s2 S0 → 4d5p 1P1 transition occurring in the Y+ ion. The complexity of this transition hindered the ability to reliably calculate the atomic mass and field shift factors, which are necessary for extraction of nuclear charge radii

Isotope shifts from collinear laser spectroscopy of doubly charged yttrium isotopes

Collinear laser spectroscopy has been performed on doubly charged ions of radioactive yttrium in order to study the isotope shifts of the 294.6-nm 5s2S1/2→5p2P1/2 line. The potential of such an alkali-metal-like transition to improve the reliability of atomic-field-shift and mass-shift factor calculations, and hence the extraction of nuclear mean-square radii, is discussed. Production of yttrium ion beams for such studies is available at the IGISOL IV Accelerator Laboratory, Jyväskylä, Finland. This newly recommissioned facility is described here in relation to the on-line study of accelerator-produced short-lived isotopes using collinear laser spectroscopy and application of the technique to doubly charged ions.peerReviewe

Proton-neutron pairing correlations in the self-conjugate nucleus 42Sc

Collinear laser spectroscopy of the N=Z=21 self-conjugate nucleus 42Sc has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-square charge radius between the Iπ=0+ ground state and the Iπ=7+ isomer via the measurement of the 42g,42mSc isomer shift. New multi-configurational Dirac-Fock calculations for the atomic mass shift and field shift factors have enabled a recalibration of the charge radii of the 42−46Sc isotopes which were measured previously. While consistent with the treatment of proton-neutron, proton-proton and neutron-neutron pairing on an equal footing, the reduction in size for the isomer is observed to be of a significantly larger magnitude than that expected from both shell-model and ab-initio calculations. The measured nuclear magnetic dipole moment and electric quadruple moment, on the other hand, are in good agreement with simple empirical estimates and shell-model calculations.peerReviewe