Abstract
The stable isotopes of xenon, which have attracted interest for a number of reasons, span a transitional region that evolves from γ-soft structures for the lighter mass isotopes to nearly spherical 136Xe with a closed neutron shell. The nature of this transition, which is gradual, is not well understood. To provide detailed spectroscopic information on the Xe isotopes, we have studied 130,132,134,136Xe at the University of Kentucky Accelerator Laboratory using inelastic neutron scattering and γ-ray detection. These measurements yielded γ-ray angular distributions, branching ratios, multipole mixing ratios, and level lifetimes (from the Doppler-shift attenuation method), which allowed the determination of reduced transition probabilities and provided insight into the structure of these nuclei.
Highlights
With seemingly so much knowledge to gain, we chose to perform inelastic neutron scattering (INS) measurements at the University of Kentucky Accelerator Laboratory (UKAL) on 130,132,134,136Xe. For each of these isotopes, highly enriched gases were converted to approximately 10 grams of solid XeF2 and γ-ray spectroscopic measurements were performed following INS with nearly monoenergetic neutrons produced by the 3H(p,n)3He reaction. Both angular distribution and excitation function measurements were performed, yielding γray thresholds, which aided in the placement of γ rays from the level of origin, spins and parities, multipole mixing ratios, and level lifetimes via the Doppler-shift attenuation method (DSAM)
Through comparison with the theoretical predictions for the reduced transition probabilites for the E(5) symmetry, it was determined that neither 130Xe, nor 132Xe is a good representation of this critical-point symmetry
It was further determined that 134Xe is not a good representation of a vibrational nucleus due to the lack of E2 strength when compared with the harmonic vibrator model [4]
Summary
The stable isotopes of xenon span a region of nuclear structure that is transitional in nature. The former interpretation was shown in the work by Radich et al [1]. In addition to being interesting from a structural point of view, these nuclei play prominent roles in the ongoing searches for neutrinoless double-beta decay (0νββ). Comprehensive structural information provides crucial tests of the nuclear structure models used in calculating the nuclear matrix element for 0νββ and the neutrino mass, if this exotic decay process is observed
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