Author Institution: Department of Chemisty, University of WashingtonWe have studied a long-known but unanalyzed system of bands in the region 360-450 nm caused by an elusive species in unsaturated sulfur at 300βC to 650βC. All vibrational band heads fit a progression of vβ²β²βΌ400cmβ1 and vβ²βΌ 640 cmβ1. The origin, located with the help of 34S, is at 23 601 cmβ1. The vapor species is here identified as S3β thiozone, because the spectrum can be obtained in a krypton matrix at 20βK and in an organic glass at 77βK when S3βCl2β is photolyzed at low temperature. A continuum in the absorption spectrum of sulfur vapor in the 530 nm region is shown to be due to S4β, which can be synthesized by the photolysis of S4βCl2β in a low temperature glass