Spectroscopy and excited-state g factors in weakly collective Cd111 : Confronting collective and microscopic models

Abstract

Background: The even cadmium isotopes near the neutron midshell have long been considered among the best examples of vibrational nuclei. However, the vibrational nature of these nuclei has been questioned based on E2 transition rates that are not consistent with vibrational excitations. In the neighbouring odd-mass nuclei, the g factors of the low-excitation collective states have been shown to be more consistent with a deformed rotational core than a vibrational core. Moving beyond the comparison of vibrational versus rotational models, recent advances in computational power have made shell-model calculations feasible for Cd isotopes. These calculations may give insights into the emergence and nature of collectivity in the Cd isotopes.Purpose: To investigate the nature of collective excitations in the A ∼ 100 region through experimental and theoretical studies of magnetic moments and electromagnetic transitions in 111 Cd. Method:The spectroscopy of 111 Cd has been studied following Coulomb excitation. Angular correlation measurements, transient-field g-factor measurements and lifetime measurements by the Doppler-broadened line shape method were performed. The structure of the nucleus was explored in relation to particle-vibration versus particlerotor interpretations. Large-scale shell-model calculations were performed with the SR88MHJM Hamiltonian.Results: Excited-state g factors have been measured, spin assignments examined and lifetimes determined. Attention was given to the reported 5/2 + 753-keV and 3/2 + 755-keV states. The 3/2 + 755-keV level was not observed; evidence is presented that the reported 3/2 + state was a misidentification of the 5/2 + 753-keV state.Conclusions: It is shown that the g factors and level structure of 111 Cd are not readily explained by the particlevibration model. A particle-rotor approach has both successes and limitations. The shell-model approach successfully reproduces much of the known low-excitation structure in 111 Cd.

Spectroscopy of Cd99 and In101 from β decays of Park1, Krücken2, Blazhev3 et al. 2020Phys. Rev. CSelf Cite

“…The effective charge set of e p = 1.7e, e n = 1.0e has been used for Cd isotopes in Refs. [28,31]. Meanwhile, the literature B(E 2) value of the (6 + 1 ) → (4 + 1 ) transition in 102 Sn [16] provides a reference for tuning of the neutron effective charge for the SR88MHJM interaction, whose proton model space is limited to Z 50.…”

E2 collectivity in shell-model calculations for odd-mass nuclei near 132Sn

“…Details of the effective charges adopted and relevant experimental data are shown in Table 1. Literature choices for the effective proton charge for the In isotopes range between e p = 1.35 [13] to e p = 1.7 [14][15][16]. A value of e p = 1.34 has been chosen for the present work based on the known lifetime of the I π = 8 + , E x = 2130 keV isomer in 130 Cd.…”

Magnetic moment of the 11/2− isomeric state in Mo99 and neutron spin g

“…Large-scale shell-model calculations for 111 Cd provided a good description of both signs and magnitudes of experimental magnetic moments for six states using a stan-dard quenching factor of 0.7 [46]. It is interesting that Refs.…”