Half-life measurements of isomeric states populated in projectile fragmentation

Abstract

The half-lives of excited isomeric states observed in 195Au, 201Tl and 215Rn are reported for the first time. Delayed γ-rays were correlated with nuclei produced in the projectile fragmentation of relativistic 238U ions, unambiguously identified in terms of their atomic number (Z) and mass-to-charge ratio (A/Q) after traversing an in-flight separator. The observation of a long-lived isomeric state in 195Au with t1/2 = 16−4+8 μs is presented. Two shorter-lived isomeric states were detected in 201Tl and 215Rn with t1/2 = 95−21+39 and 57−12+21 ns respectively. In total 24 isomeric states were identified in different nuclei from Pt to Rn (A ∼ 200) during the current study, the majority of which were previously reported. The wealth of spectroscopic data provides the opportunity to determine the isomeric ratios over a wide range of Z, A and angular momentum (I ħ) of the reaction products. In particular, high-spin states with I ≳ 18 ħ provide a robust test of theoretical models of fragmentation.