Abstract
In-situ powder X-ray diffraction patterns of two sample mixtures of elemental Cs and molecular hydrogen in a diamond anvil cell were recorded using synchrotron radiation at elevated pressure and temperature. The formation of several mixed phased molecular complexes was evident. In one sample, the X-ray diffraction pattern recorded at 6.7 GPa showed a remarkable resemblance to that of the clathrate hydrate structure by a full-pattern refinement. For both samples, successive structural transformations were observed with increasing pressure and temperature, upon laser heating. Apart from unreacted H2, Raman measurements on the second sample revealed a new H2 mode in the vibronic spectral range. The pressure variation of the second vibronic branch is consistent with H2 molecules trapped in an encaged environment.
