Half-life measurements of isomeric states populated in projectile fragmentation

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 t_1/2=16_-4⁺⁸ μs is presented. Two shorter-lived isomeric states were detected in ²⁰¹Tl and ²¹⁵Rn with t_1/2=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 h) of the reaction products. In particular, high-spin states with I ≳ 18 h provide a robust test of theoretical models of fragmentation.