Ionic Paramagnetic Species Associated with γ-Irradiated Amyl Disulfide

Abstract

ESR and optical bleaching studies of n‐amyl disulfide, γ‐irradiated at 77°K in the amorphous state indicate the presence of ionic paramagnetic species in the irradiated material involving unpaired spins localized mainly at the sulfur. A comparison of ESR derivative peak positions from such samples with those arising from an apparent negative ion species produced from amyl disulfide in a tetrahydrofuran matrix indicates that this species may be common to both types of samples. This finding is supported by the fact that the threshold energy for the destruction of the ionic centers by optical bleaching is the same for both types of samples, being 2.1±0.2 eV. If the ESR spectrum of the negative‐ion species is substracted from the initial ionic species spectrum of amorphous amyl disulfide an ESR line shape is obtained which is postulated to result from a positive‐ion species. The principal g values obtained for this species are 2.003±0.001, 2.035±0.001, and approximately 2.018. Calculated g values based on a model in which the electron hole is localized on a nonbonding 3p sulfur orbital are in qualitative agreement with the observed g values. The The negative‐ion species appearing to be common to both types of samples exhibits an axially symmetric g tensor (g‖ = 2.003±0.001, g_⊥ = 2.022±0.001). This g tensor symmetry is obtained theoretically using a model in which the unpaired spin is in 3dσ bonding orbitals associated with both sulfurs.