Optical Absorption and X-Ray Diffraction Studies of Sulfur Under High Pressure

In situ high pressure optical absorption measurements of sulfur have been carried out by using DAC device with a TASCO V-550 UV-VIS spectrophotometer at pressures up to 41.6 GPa.The curves of absorption edge vs pressure were obtained,in which there are two turning points at about 5 and 12 GPa,corresponding to two changes of colour in the optical observation:one is from yellow to red and the other from red to black at 5-6.5 and 10-12 GPa,respectively.The absorption edge reaches above 800 nm when the pressure is increased to 23 GPa.The structure and phase transitions have also been investigated by using in situ high pressure energy-dispersive x-ray diffraction with synchrotron radiation at pressures up to 33.7 GPa.No structure phase transition occurs at 5-6 GPa,but there is a new high-pressure phase,caused probably by the reorieutation or ordering of Sq.