The Mass Excesses of 91Tc and 90Tc

Abstract

The isotopes 91Tc and 90Tc have been identified by β- and γ-ray spectroscopy. The 91Tc ground state decays with a half-life of 3.12 ± 0.05 min, and has been assigned a Jπ of 9/2+. Two isomers in 90Tc with half-lives of 7.9 ± 0.2 s and 50 ± 2 s have been identified for the first time. The Jπ for the 7.9 s isomer has been deduced as 1+. The mass excess for 91Tc has been determined to be −76.0 ± 0.2 MeV, and the mass excess corresponding to the 7.9 s isomer in 90Tc has been determined to be −71.2 ±.2 eV.