Investigation of short-lived isomeric states with half-lives in the μs and ms region

Abstract

Unique experimental isotope assignments are presented for fifteen previously reported isomeric states with half-lives in the μsec and msec region. The isomers were produced by photonuclear reactions. The assigned activities are 49.5 μsec Sc 44m, 10.2 μsec Co 58m, 5.1 μsec Ge 69m, 17.5 μsec Ru 101m, 1.7 msec Ru 103m, 155 μsec Sn 115m, 49 μsec Hf 175m, 10.5 μsec Hf 176m, 8.3 μsec Hf 177m, 70 μsec Re 186m, 225 μsec Os 187m, 92 μsec Hg 203m, 21 μsec Hg 203m, 2.1 msec Tl 201m and 62 μsec Tl 204m. A few of these assignments have been previously suggested in the literature on a tentative basis. The isotope assignments of the following three short-lived activities remained ambiguous; 11.5 μsec Ru 100m or Tc 100m, 710 μsec Ru 101m or Tc 101m and 10.4 μsec Cd 109m or Ag 109m. In addition, a new 435 μsec isomeric state in Sc 43 and a new 18 μsec isomeric state in Hf 177 were discovered. Additional results include improved values for half-lived and gamma-ray energies for these isomeric transitions, and detailed measurements on the decay properties of some of the reported short-lived isomeric states. The multipolarities of a few of the observed transitions were determined.