Are photo-induced crystalline sulfur and S-II equivalent under high pressure?

Abstract

Sulfur is known to be a photo-sensitive material. Photo-induced crystalline sulfur (p-S) was found in high-pressure Raman studies more than two decades ago. However, its structureremains not well understood. In this work, a thin α-S8 crystal was pressurized to 8 GPa in a diamond anvil cell (DAC) and its surface was repeatedly scanned by a 532 nm laser to produce the largest possible amount of p-S. A high-quality XRD pattern of p-S was obtained for the first time. The refinement of experimental data indicated the structural consistency between p-S and high-pressure and high-temperature (HPHT) S-II phases. Moreover, HPHT experiments were conducted to study the effect of temperature on p-S formation. The current work provides a strategy for producing the high-purity photo-induced product. The combination of synchrotron XRD, Raman spectroscopy, and microscopical imaging technology shows an effective way for photochemical research.