Jennifer J. Ressler

SASSYER: An old instrument for new physics at Yale

Abstract The Wright Nuclear Structure Laboratory has recently acquired a gas-filled recoil separator previously used at Berkeley National Laboratory for heavy-element synthesis. The separator will be used to separate reaction recoils from primary beam particles and fission products following target bombardment. Commissioning of the separator has recently been completed, and the structure of 203 Rn investigated.

Isomers and seniority in the trans-Pb nuclei

Low-energy excited states of 210 Ra and 208 Ra were investigated at the Wright Nuclear Structure Laboratory of Yale University. Fusion evaporation recoils were selected using the gas-filled spectrometer, SASSYER. Delayed γ-rays, following isomeric decays, were detected at the focal plane of SASSYER with a small array of HPGe detectors. Transitions following the proposed J π = 8 + isomers were observed, and the half-lives measured. The experiments are discussed and results compared to expectations from the seniority scheme.

Surrogate Nuclear Reactions using STARS

The results from two surrogate reaction experiments using the STARS (Silicon Telescope Array for Reaction Studies) spectrometer are presented. The surrogate method involves measuring the particle and/or γ‐ray decay probabilities of excited nuclei populated via a direct reaction. These probabilities can then be used to deduce neutron‐induced reaction cross sections that lead to the same compound nuclei. In the first experiment STARS coupled to the GAMMASPHERE γ‐ray spectrometer successfully reproduce surrogate (n,γ), (n,n′γ) and (n,2nγ) cross sections on 155,156Gd using 3He‐induced reactions. In the second series of experiments an energetic deuteron beam from the ESTU tandem at the Wright Nuclear Structure Lab at Yale University was used to obtain the ratio of fission probabilities for 238U/236U and 237U/239U populated using the 236,238U(d,d′f) and 236,238U(d,pf) reactions. Results from these experiments are presented and the implications for the surrogate reaction technique are discussed.

Gamma-ray Spectroscopy of 132Te through Beta Decay of a 132Sb Radioactive Beam

{gamma}-ray spectroscopy of {sup 132}Te, obtained from {beta}{sup -} decay of a {sup 132}Sb radioactive beam at the Holifield Radioactive Ion Beam Facility, was performed using the Clarion array. A significantly revised {gamma}-decay scheme for {sup 132}Te was obtained including a number of new, likely 2{sup +}, states below 2.5 MeV and the removal of a 3{sup -} state at 2280 keV. A simple shell-model interpretation is discussed for the low-lying levels.

Limits Of The Energy‐Spin Phase Space Beyond The Proton Drip Line: Entry Distributions Of Pt And Au Isobars

The systematic study of entry distributions populating proton‐rich Pt and Au isotopes indicates a limit in the excitation energy and angular momentum in the population of 173Au, a nucleus beyond the proton drip line.

The Highs And Lows Of The A=100 Region: Vibration-To-Rotation Evolution In Mo And Ru Isotopes

Nuclei below the Z = 50 magic shell gap with A∼100 show a wide variety of structural phenomena. These include excellent examples of vibrational collectivity at low-spins, which give way to more rotational-like excitations with increasing angular momentum. In this paper we present recent results from an experiment performed at Yale to study the yrast evolution of states in 98,99 Mo and 101,102 Ru. Although the high-spin data is consistent with predictions from rotational model theories, we propose a simple presciption to distinguish between vibrational and rotational regimes of angular momentum generation. When applied to the nuclei of interest, a clear picture emerges of how these two mechanisms of collective spin generation compete in this region.

SASSYER: A Gas‐filled spectrometer at Yale

The Wright Nuclear Structure Laboratory has recently acquired a gas‐filled recoil separator previously used at Berkeley National Laboratory for heavy‐element synthesis. The separator will be used to separate reaction recoils from primary beam particles and fission products following target bombardment. Commisioning of the separator has recently been completed, and the structure of 203Rn investigated.