Excited Levels in ¹⁹⁰Hg and a 24.5 ns Isomer

Abstract

Time distributions of γ-rays from the ¹⁸¹Ta(¹⁴N, 5n)¹⁹⁰Hg reaction were observed between natural beam bunches of a cyclotron. Excitation functions and anisotropies of γ-rays were also measured. The 418 keV (2⁺→0⁺), 626 keV (4⁺→2⁺), and 723 keV (6⁺→4⁺) γ-rays from ¹⁹⁰Hg have been found to decay with a half-life, T_1⁄2=24.5±0.7 ns. A new level scheme of ¹⁹⁰Hg is proposed; the 8⁺, 7⁻, and 5⁻ levels are placed at 2468, 2016, and 1828 keV, respectively, and the 24.5 ns isomer is assigned to a 10⁺ state tentatively placed at 2604 keV.