Isolated hydrogen molecules in GaAS

Molecular hydrogen was directly observed in crystalline GaAs by Raman spectroscopy. At Tau = 77 K, GaAs samples that have been exposed to a hydrogen/deuterium plasma exhibit four vibrational lines at 2842.6, 3446.5. 3925.9, and 3934.1 cm (exp -1), respectively. With a pure hydrogen plasma only the two high frequency lines can be seen and with a pure deuterium plasma only the lowest frequency is observed. We attribute these frequencies to the rovibrational modes of isolated interstitial D2, HD, and H2 molecules, respectively.