Resonance conversion as a dominant decay mode for the 3.5-eV isomer in 229m Th

on the basis of calculations performed withi nthe relativistic multiconfiguration Dirac-Fock method, it is shown that the probability of the decay of the 3.5-eV nuclear level in the 229 m Th isomer via resonance conversion exceeds the probability of its direct radiative decay by at least a factor of about 600. The possibility of experimentally observing delayed soft photons or alpha particles in the decay of this isomer is discussed.