Isomeric states observed in heavy neutron-rich nuclei populated in the fragmentation of a208Pb beam

Abstract

Heavy neutron-rich nuclei were populated via the fragmentation of a E/A = 1 GeV 208 82 Pb beam. Secondary fragments were separated and identified and subsequently implanted in a passive stopper. By the detection of delayed γ rays, isomeric decays associated with these nuclei have been identified. A total of 49 isomers were detected, with the majority of them observed for the first time. The newly discovered isomers are in 204,205 80 Hg, 201,202,204,205 79 Au, 197,203,204 78 Pt, 195,[199][200][201][202][203] 193,[197][198][199] 196 75 Re, 190,191 74 W, and 189 73 Ta. Possible level schemes are constructed and the structure of the nuclei discussed. To aid the interpretation, shell-model as well as BCS calculations were performed.

Long-lived isomers in neutron-richZ=72–76 nuclides

“…A low-lying 13/2 + isomer is expected to occur in 195 Os, but this has not been identified in previous experiments on this nucleus [13]. We now present evidence for the identification of a long-lived isomer which is populated more strongly than the ground state, with 73 isomeric ions and 63 ground-state ions observed.…”

“…This is largely due to the fragment ions, in the main, being fully stripped of atomic electrons. To date, projectile fragmentation in combination with in-flight fragment separation has enabled microsecond isomers to be found some distance from the line of stability [11][12][13], through the emission of time-correlated gamma rays. The detection of long-lived isomers however, is not possible with that technique.…”

Review of metastable states in heavy nuclei

“…[415,416,417,418]). The early studies were somewhat limited in terms of the extent of firm spectroscopic information, although the situation continues to develop with the incorporation of more powerful γ-ray detections systems such as used in the RISING campaign [419].…”

“…The early studies were somewhat limited in terms of the extent of firm spectroscopic information, although the situation continues to develop with the incorporation of more powerful γ-ray detections systems such as used in the RISING campaign [419]. Figure 23 is an example of the reach of these reactions for populating neutron-rich nuclei, resulting in the discovery of numerous isomers [416]. Studies of the high-spin population in terms of isomeric ratios indicate more favouring of higher-spins than expected [412,420], reaching spins of ≤ 55/2 .…”

Isomer Decay Spectroscopy ofSm164andGd166Patel1, Söderström2, Podolyák3 et al. 2014Phys. Rev. Lett.Self Cite589380View full textAdd to dashboardCite

“…In order to extend the experimental knowledge, and to test more recent theoretical calculations [10], we exploit a basic nuclear structure feature, namely, that deformation gives rise to long-lived nuclear excited states (isomers) [11]. Isomers with half-lives in the 100 ns to 100 μs range allow highly sensitive access to nuclear excited states following relativistic heavy-ion reactions [12]. Combined with the excellent uranium beam intensities from the Radioactive Ion Beam Factory (RIBF) facility at RIKEN, Japan [13], we have been able to reach further into the A ¼ 160-170 midshell neutron-rich domain than was previously possible.…”