The Optical Absorption Spectrum of Fluid Sulfur up to Supercritical Conditions

Optical absorption spectra in the range 0.5–4.9 eV (250 to 2000 nm) are reported for fluid sulfur up to 1100°C and at pressures up to supercritical pressures. An absorption band at 360 nm at 145°C is attributed to a few percent cyclo‐S6 (c‐S6) in the predominantly cyclo‐S8 (c‐S8) liquid. No anomaly in the rate of red shift of the absorption edge is observed at the polymerization temperature (160°C). Above this temperature an absorption band due to diradical chains is observed at low energy (∼1.4 eV). Investigation of the density dependence of the spectra of the dense fluid results from overlapping bands due to c‐S8, S3, and S4.