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Title: Collinear laser spectroscopy of manganese isotopes using the radio frequency quadrupole cooler and buncher at ISOLDE
Author: Babcock, Carla
ISNI:       0000 0004 6058 2540
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2015
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The hyperfine structure of the odd-even ⁵¹⁻⁶³Mn isotopes (N = 26 - 38) were measured using bunched beam collinear laser spectroscopy with the COLLAPS experimental setup at ISOLDE, CERN. The properties of these nuclei were investigated over the course of two experiments. During the first experiment, nuclear spins and magnetic dipole moments were extacted from spectroscopy on manganese atoms. These nuclear properties were then compared to the predictions of two large-scale shell model effective interactions (GXPF1A [1, 2] and LNPS [3]) which use different model spaces. In the case of 61,63Mn, these results show the increasing importance of neutron excitations across the proposed N = 40 subshell closure, and of proton excitations across the Z = 28 shell gap. These measurements provide the first direct proof that proton and neutron excitations across shell gaps are playing an important role in the ground state wave functions of the neutron-rich Mn isotopes. The electric quadrupole moment provides complementary information to the magnetic dipole moment, since it is able to directly probe the degree of collectivity and deformation in a nucleus, however sensitivity limitations during the first experiment prevented the quadrupole moments from being accurately determined. To overcome these limitations, it was necessary to find an electronic transition with sensitivity to the quadrupole interaction. A suitable transition was found in the ion from a metastable state and optical pumping in ISOLDE's cooler and buncher, ISCOOL, was used to populate this state for the second manganese experiment. This is the first use of the in-cooler optical pumping technique at ISOLDE, and required an overhaul of ISCOOL. During the second experiment, the spectroscopic quadrupole moments of the isotopes were extracted from the measured hyperfine spectra of manganese ions. The sensitivity and spectroscopic efficiency were increased as compared to the atomic experiment. The extracted quadrupole moments were again compared to predictions from the GXPF1A and LNPS effective interactions. The inclusion of the 1 vgg/2 and 2 vd5/2 orbitals in the model space were shown to be necessary to reproduce the experimentally observed onset of quadrupole deformation.
Supervisor: Cheal, B. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral