Variable-time neutralization-reionization mass spectrometry is used to generate isotopomers of metastable hydrosulfonium radicals, H3S., of lifetimes ranging between 0.2 and 2.8 mu s. The fractions of metastable (H3S.)-S-32, (H3S.)-S-34, (D3S.)-S-32, (D3S.)-S-34, and (D2HS.)-S-32 increase with the increasing internal energy of the precursor cations. Intramolecular isotope effects favor less of H from D2HS.. Ab initio calculations at the MP2/6-311++G-(3df,2p) level indicate existence of symmetry-restricted (2)A’ and (2)A " electronic stales of H3S.. Formation of metastable radicals from vibrationally excited precursor ions is discussed.