New proton radioactivities165,166,167Irand

Abstract

The new proton radioactivities 165,166,167 Ir and 171 Au have been observed. The Ir isotopes were produced via the 92 Mo( 78 Kr,pxn) 165,166,167 Ir reactions at 357 and 384 MeV. 171 Au was produced via the 96 Ru( 78 Kr,p2n) 171 Au reaction at 389 MeV. The proton emitters were each identified by position, time, and energy correlations between the implantation of a residual nucleus into a double-sided silicon strip detector, the observation of a decay proton, and the subsequent observation of a decay alpha particle from the daughter nucleus ͑ 164,165,166 Os and 170 Pt, respectively͒. Both 166 Ir and 167 Ir have proton-emitting ground and isomeric states, which also decay by alpha emission. The proton-decay rates have been reproduced by calculations using the WKB barrier penetration approximation and a low-seniority shell-model calculation of the spectroscopic factors. The alpha decays of the four nuclei are followed by chains of alpha decays, allowing the determination of single-particle orbital orderings. Mass information has also been obtained from the alpha-decay chains because a connection to a known mass can be obtained for one of the nuclei. Ground-state mass excesses are reported for 151 Tm, 154 Yb, 155 Lu, 158 Hf, 159 Ta, 162 W, 163 Re, 166 Os, 167 Ir, and 170 Pt. The mass excess for 171m Au is also given. Proton separation energies are also deduced for the odd-Z alpha daughter nuclei of the Ir proton emitters.

Exploring the Limits of Stability

“…[117] in 2002, and although apparently a contribution to a conference it was not identified as such. This nucleus has not been reported in a regular refereed publication since, so it was omitted from the present compilation and 165 Ir first observed in 1997 is still the lightest iridium isotope [103]. A compilation based on a literature search as the present one is probably not perfect.…”

Collective excitations in the transitional nucleiRe163andRe165

“…The recoil-decay time correlation was limited to 214 ms to reduce false correlations with the dominant reaction channel 163 W, which has a longer α-decay half-life, t 1/2 = 2800(170) ms [27]. − state was measured to be 115.1(40) keV in previous work by Davids et al [26].…”

How far from stability can we go using Gammasphere and the ANL Fragment Mass Analyzer?

“…These nuclei lie beyond the proton drip line (Qp L 0) and are kept bound by the coulomb force. A number of new proton emitters have been identified recently using the FMA [6], and the lifetimes in nearly all of these cases can be well reproduced by WKB calculations using spectroscopic factors derived from spherical shell model calculations. This allows for definitive single-particle assignments to be given to the proton-emitting states.…”

“…Several such experiments have been performed, and two of them are described briefly below. The two known alpha-emitting states in 1671rwere recently found to proton decay as well [6]. Based on the partial half-lives, the ground state was given an S112assign-ment while the isomeric state at 175 keV was assigned to the h11i2 configuration.…”