Vibrational Dynamics of Hydrazine to 50 GPa.

Raman, mid-infrared, and far-infrared spectroscopy have been used to investigate pressure-induced phase transitions, changes in hydrogen bonding, and intermolecular interactions of hydrazine up to 50 GPa. Mid-infrared measurements show splitting in the symmetric and asymmetric N-H stretching vibration bands near a phase transition at 30 GPa, indicating a change in hydrogen bonding. The transition exhibits a large hysteresis loop of ~20 GPa on decompression. Far-infrared measurements reveal splittings and the appearance of new peaks. Raman measurements show lattice vibrational modes splitting and broadening near the phase transitions at 20 and 30 GPa. The results are compared with x-ray diffraction data and first principles simulations.