INFRARED-SPECTRA AND STRUCTURES OF ISOTOPICALLY ENRICHED S3 AND S4 IN SOLID ARGON

Sulfur vapor was seeded into a microwave-powered argon discharge and condensed at 12 K. Infrared spectra revealed sharp strong bands at 690.0, 676.2, 661.6, and 642,4 cm-1, which were also observed by thermal dissociation of S8 flowing in a quartz tube heated to 400-900-degrees-C. Increasing the sulfur concentration in the discharge favored the latter two relative to the former two absorptions. Enriched S-34 samples gave isotopic shifts for pure sulfur fundamentals and isotopic multiplets that identify these species. Sample annealing produced a strong S2 chemiluminescence and a sharp new 674.5-cm-1 band. This feature revealed a sharp 1/2/1/1/2/1 sextet with 50/50 S-32/S-34, which confirms the observation of C2-nu thiozone; similar multiplets were found for the 680.0- and 676.2-cm-1 bands. Calculations from four pairs of symmetrical isotopic nu-3 values gave 116 +/- 2-degrees for the valence angle. The 661.6- and 642.4-cm-1 absorptions behaved differently in the experiments and revealed isotopic multiplets appropriate for S4; these absorptions are assigned to two different open-chain S4 isomers. Weaker bands at 720.5 and 710.1 cm-1, which appeared on annealing, are assigned to (S2)2 dimer species.