RAMAN SPECTRUM AND FORCE CONSTANTS OF S42-

Raman spectroscopy using a He-Ne laser as excitation source has been used to identify a new species of molecular sulfur in concentrated aqueous solutions of sulfur in sodium sulfide. A normal coordinate vibrational analysis has been performed based on a non-linear four-atom model having SS bond lengths = 2.04 A ̊, SSS bond angles = 105°, and the SSSS dihedral angle = 90°. The potential function used was the internal-rotation-excluded version of the Mizushima-Morino potential (1) and the force constants were the generalized valence forces derived by Venkateswarlu and Thirugnanasambandam (2) from a normal coordinate analysis of the S8 molecule. Excellent agreement between observed and predicted Raman shifts and polarization characteristics was obtained. The four-atom species is presumably present in aqueous solution as the S42- dianion. The mechanism of crystallization of rhombic sulfur and trigonal selenium from solutions in sodium sulfide is discussed in terms of this tetra-atomic species. © 1969.