Orientational dynamics and disorder of solid adamantane as studied by infrared spectroscopy

摘要

The CH stretching and bending vibrations of isotopically dilute C10D15H in a host crystal of perdeuterated adamantane have been monitored by infrared spectroscopy as a function of temperature from 7 to 300 K. The infrared bands depend upon both intramolecular and intermolecular interactions. The intramolecular splittings of the bands have been analyzed and compared with normal coordinate calculations. The intermolecular splittings of the CH stretches in the tetragonal phase are found to collapse and broaden with increasing temperature due to librational motion. A Redfield theory analysis of the temperature dependent line shifts and linewidths yields a correlation time of 2 ps for the adamantane libration. In the disordered plastic phase of adamantane, the intermolecular and intramolecular splittings of the CH stretches disappear and the rotational disorder yields a broad inhomogeneous band.