Detailed spectroscopy of110Cd: Evidence for weak mixing and the emergence ofγ-soft behavior

Abstract

A study of the β + /EC decay of 110 In into levels of 110 Cd is combined with a reanalysis of data from a previous study of 110 Cd with the (n, n ′ γ) reaction with monoenergetic neutrons. The γγ coincidences from the 110 In decay leads to many new assignments of γ rays observed in the (n, n ′ γ) reaction, permitting the observation of weak low-energy transitions, and setting stringent upper limits on unobserved decay branches. The uncertainties on many of the lifetimes from the (n, n ′ γ) reaction are significantly reduced, and limits are established for the lifetimes of levels too long for a direct measurement. The absence of enhanced transitions between the previously assigned phonon states and the deformed intruder states strongly suggests that mixing between the configurations is generally weak, refuting the strong-mixing scenario as an explanation of the decay pattern of the excited 0 + states in 110 Cd. The decay pattern of the non-intruder states is suggestive of a γ-soft rotor, or O(6) nucleus, rather than a vibrational, or U (5) pattern. The existence of a 4p − 6h proton excitation in 110 Cd is also suggested.

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

“…Later, the presence of intruder states, due to the 2-particle 4-hole proton excitations near the nominal two-phonon triplet, was included through configuration mixing [7][8][9]. Recently, however, it has been found that this interpretation, based on an anharmonic vibrator model with strong intruder mixing, is not consistent with experimental electromagnetic transition rates [10][11][12][13][14][15]. The confrontation between theory and experiment in the Cd isotopes has sparked a more general debate over the nature of nuclei that are not clearly deformed rotors [16,17].…”

q-deformed vibrational limit of interacting boson model

“…The even-even Cd isotopes have long been considered one of the main examples of vibrational behavior. Recently, experimental studies have indicated significant deviations from this behavior, in selected two-and three-phonon states, along the Cd chain (A=108-126) [9,10]. Re-examination of the structure of the midshell Cd isotopes suggests that they may represent ( ) O 6 deformed γ-soft rotors rather than ( ) U 5 spherical vibrators.…”

Partial dynamical symmetry and the vibrational structure of Cd isotopes

“…Recently, advanced experimental studies have reported significant deviations from this behaviour in selected two-and threephonon states, along the Cd chain (A=108-126) [1][2][3]. These observations have led to claims for the "breakdown of the vibrational motion" in these isotopes and the need for a paradigm shift [1,2]. In the present contribution, we examine an alternative explanation for the structure of the Cd isotopes, in terms of U(5) partial dynamical symmetry (PDS) [4].…”

“…The Cd isotopes have been traditionally considered to be a prime example of spherical vibrators. Recently, advanced experimental studies have reported significant deviations from this behaviour in selected two-and threephonon states, along the Cd chain (A=108-126) [1][2][3]. These observations have led to claims for the "breakdown of the vibrational motion" in these isotopes and the need for a paradigm shift [1,2].…”

“…Absolute B(E2) values for transitions from the 0 + 4 state are not known, but its branching ratio to 2 + 2 is small. Attempts to explain the above deviations in terms of strong mixing between the normal spherical [U(5)-like] states and intruder deformed [SO(6)-like] states have been shown to be unsatisfactory [1,2]. The reasons are twofold.…”