On a problem of assumed ^232mPa isomer characteristics

Abstract
To study fission characteristics of protactinium-232, the isotope under investigation was built up in the ²³²Th(p, n) reaction at a proton energy of E_p ≈ 11.5 MeV. At irradiating the layer by thermal and resonance neutrons the short-lived components with a half-decay period of ~ 6 hours were found in the yields of fission fragments. The totality of experimental data can be explained by the fact that at the thorium-232 bombardment by accelerated protons the protactinium-232 nuclei are formed in the isomer state with a half-life of T_1/2 ≈ 2.3 hour. The isomer of ²³²mPa decays approximately with the similar probability by isomer transition to the ground state ²³²Pa and, as a result of α-decay, to the isotope ²²⁸Ac (T_1/2 = 6.15 hour).