Infrared spectra of HSCS⁺, c-HSCS, and HCS₂ ^- produced on electron bombardment of CS₂ in solid para-hydrogen

We report infrared (IR) spectra of HSCS⁺, c-HSCS, HCS₂^-, and other species produced on electron bombardment of a mixture of CS₂ and para-hydrogen (p-H₂) during deposition at 3.2 K. After maintenance of the deposited matrix in darkness for 12 h, the intensities of the absorption lines of HSCS⁺ at 2477.2 (ν₁), 1525.6 (ν₂), and 919.6 cm^-1 (ν₃) decreased through neutralization of HSCS⁺ with trapped electrons. During this period, the intensities of the lines of HCS₂^- at 2875.7 (ν₁), 1249.9 (ν₅), 1003.2 (ν₆), and 814.3 cm^-1 (ν₄) increased due to reaction between H and CS₂^-. The intensities of the lines observed at 2312.7 and 889.0 cm^-1, which are assigned to the c-HSCS radical, increased after maintenance in darkness and greatly diminished after irradiation at 373 nm. The IR spectra of HSCS⁺, HCS₂^-, and c-HSCS are reported for the first time. The IR absorption lines of the t-HSCS radical, t-HC(S)SH, and c-HC(S)SH were also identified; their wavenumbers are similar to those reported for these species in an Ar matrix. The corresponding spectra of the ¹³C, ³⁴S, and D isotopic variants of these species were observed. The assignments were made according to the expected chemical behavior, predicted potential energies of associated reactions, and a comparison of observed and predicted wavenumbers and their ¹³C, ³⁴S, and D isotopic ratios. In contrast to the observed significant red shifts of the OH-stretching wavenumbers of HOCO⁺ and HOCS⁺ in solid p-H₂ compared to those in the gaseous phase due to proton sharing with H₂, the wavenumber of the HS-stretching mode of HSCS⁺ in solid p-H₂ (2477.2 cm^-1) is similar to the anharmonic wavenumber of HSCS⁺ (2424 cm^-1) predicted with the B3LYP/aug-cc-pVTZ method, indicating that the sharing of a proton between HSCS⁺ and neighboring H₂ molecules is insignificant.