Molecular Species in Orthorhombic Selenium

The Raman and infrared spectra of orthorhombic selenium were measured. The spectra are not explained by any structural models assuming the presence of hitherto-known molecules, that is, polymeric chains, Se6 rings, and Se8 rings. This suggests that orthorhombic selenium consists of unknown molecular species. This is supported by the experimental result that only the orthorhombic form can be recrystallized from a solution of orthorhombic selenium in carbon disulfide. The probability of the existence of Se7 ring molecules in orthorhombic selenium is discussed.