Particle-core Couplings Close to Neutron-rich Doubly-magic Nuclei

Abstract

Preliminary results are presented from a recent campaign of experiments, performed at the PF1B cold-neutron facility at ILL (Grenoble, France), in which γ-ray spectroscopy of neutron-rich nuclei produced in neutron induced fission on 235 U and 241 Pu targets was performed. By using the EXILL array, consisting of EXOGAM, GASP and ILL-Clover detectors, and a digital triggerless data acquisition system, γ coincidences over several microseconds time windows were studied. This allowed to obtain new information on nuclei around 132 Sn, such as 132 Te, 133 Sb and 130 Sn, in which microsecond isomeric states occur. Preliminary results on 210 Bi, populated by cold-neutron capture, are also shown. The data offer the possibility to investigate the couplings between core excitations and valence particles, around the doubly magic nuclei 132 Sn and 208 Pb.

Interplay between collective and single particle excitations around neutron-rich doubly-magic nuclei

“…3), with the cold neutron capture reaction 209 Bi(n,γ) 210 Bi [8]. From the capture state, at 4605 keV, the γ decay of 210 Bi was found to proceeds through many paths, feeding a large number of levels.…”

“…This paper will present the experimental situation in nuclei lying in close proximity of doubly-magic systems, such as 47,49 Ca [6,7], 133 Sb [8] and 210 Bi [8]. Additional examples around semi-magic systems can be found in Refs.…”

A high-energy, high-flux source of gamma-rays from all-optical non-linear Thomson scattering

“…This means that nuclear scientist can conduct experiments using a source with a peak brilliance 10 20 10 23 s −1 mm −2 mrad −2 0.1%BW [55,56]. Already, users of the facility are planing to exploit this unique opportunity to conduct experiments in photofission [57] and particle core couplings in 'doubly magic' nuclei [58]. However, this is just the beginning of the possible applications of this type of alloptical source and with improvements in the LWFA technology being developed, there could be the opportunity to further enhance the energies achievable in this type of arrangement.…”

The mutable nature of particle-core excitations with spin in the one-valence-proton nucleus 133 Sb

“…The campaign, named EXILL, lasted two reactor cycles (each ≈50 days long) and its main part consisted of two long runs of neutron induced fission on 235 U and 241 Pu targets. The use of a fully digital, triggerless acquisition system (with time stamp intervals of 10 ns) allowed event rates up to 0.84 MHz to be handled and to study coincidences among γ transitions separated in time by several tens of microseconds [44] -with analogue electronics, coincidences only across a few µs isomers could be studied with large Ge arrays. In 133 Sb, the 21/2 + isomeric state decays via a cascade of five transitions: an unknown isomeric transition with E γ < 30 keV followed by 62, 162, 1510 and 2792 keV γ rays that feed the 7/2 + ground state (see Fig.…”