Particle-rotor versus particle-vibration features ingfactors ofCd111andCd113

Abstract

The emergence and evolution of collective excitations in complex nuclei remains a central problem in the quest to understand the nuclear many-body problem. Nuclear quadrupole collectivity is usually investigated via electric quadrupole observables. Here, however, we measure the g factors of low-excitation states in 111 Cd and 113 Cd and show that they are sensitive to the nature of the collectivity in these nuclei in ways that the electric quadrupole observables are not. The particle-vibration model, which assumes spherical core excitations, cannot explain the g factors, whereas a particle-rotor model with a small, nonzero core deformation does. The contrast of the two models is made stark by the fact that they begin from the same limiting g-factor values: It is shown that when an odd nucleon occupies a spherical orbit with angular momentum j = 1/2, or a deformed orbit with j = 1/2 parentage, the particle-vibration model and the particle-rotor model both reduce to the same g-factor value in their respective limits of zero particle-vibration coupling or zero deformation.

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

“…It follows an earlier study in which it was shown that for both 111 Cd and 113 Cd, the g factors of the 1/2 + ground-states, and the strongly Coulombexcited low-lying 3/2 + and 5/2 + levels are consistent with a particle-plus-rotor description whereas the signs of the g factors of the 5/2 + states are incompatible with the particle-vibrational model [23]. Contrasting with this observation, a 3/2 + state at 681 keV in 113 Cd was excited with sufficient intensity to determine its g factor, giving g = +1.4(4) [23]. Such a large g factor in a collective odd-N nuclide is difficult to explain unless it is associated with the coupling of an odd-neutron in the νs 1/2 orbit to a spherical 2 + core excitation.…”

“…This nucleus lies between 110 Cd and 112 Cd, both of which have been considered textbook examples of vibrational nuclei [1,22]. It follows an earlier study in which it was shown that for both 111 Cd and 113 Cd, the g factors of the 1/2 + ground-states, and the strongly Coulombexcited low-lying 3/2 + and 5/2 + levels are consistent with a particle-plus-rotor description whereas the signs of the g factors of the 5/2 + states are incompatible with the particle-vibrational model [23]. Contrasting with this observation, a 3/2 + state at 681 keV in 113 Cd was excited with sufficient intensity to determine its g factor, giving g = +1.4(4) [23].…”

“…As reported in Ref. [27], the transient-field strength for Cd in iron is calibrated relative to g(2 + 1 ; 106 Pd) = +0.393 (23) [27]. The red, starred transition corresponds to the single peak at 752.8 keV.…”

Emerging nuclear collectivity in 124−130Te

“…They can be compared to the Cd isotopes (Z=48) with two proton holes, which have been more extensively studied. There is an ongoing discussion on the nature of the collectivity that, in the Cd isotopes, is traditionally associated with anharmonic vibrations [1][2][3][4][5][6].…”

Magnetic moment and lifetime measurements of Coulomb-excited states inCd106

“…However, experiments on Cd isotopes carried out by Garrett [1,2], Ekström [3] and Stuchbery [4], among others, suggest a more complex nuclear structure for some Cd nuclei, including the existence of deformation with consequent rotational motion.…”