EXTENDED INFRARED STUDIES OF HIGH-PRESSURE HYDROGEN

We have studied solid molecular hydrogen down to liquid helium tempera tures and to a pressure of 191 GPa in a new spectroscopic system, exte nding The low frequency limit by more than a factor of 3, from 3000 to 1000 cm(-1) No evidence for the earlier reported Drude behavior is fo und within our range of study; a possible explanation of this earlier report is presented. We find a new lattice mode which may be important for determining the structure of the high pressure A phase. Observati on of an IR active vibron in the A phase of parahydrogen sets restrict ions on the phase diagram.