Excitation of the Ta-180m isomer in (gamma,n) reactions and its astrophysical relevance

The yield has been determined for the excitation of (180)gTa (J(pi) = 1(+)) from the Ta-181(gamma,n) reaction by measurements of gamma rays emitted fo llowing the electron capture and beta-decays of the 8.15 h ground state. Th e probability sigma(m)/(sigma(m) + sigma(g)) for the production of the (180 )mTa isomer (J(pi) = 9(-)) after gamma absorption in the energy region from 8 to 13 MeV was deduced. The role of the initial and final spins on the re action yield, along with the relevance for nucleosynthesis of (180)mTa, is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.