Infrared Intensity Measurements of Cryodeposited Thin Films of NH ₃ , NH ₄ HS, H ₂ S, and Assignments of Absorption Bands

Abstract

Interferometric infrared spectral transmission measurements from 60 to 10 000 cm −1 were made for thin films of NH 3 , NH 4 HS, and H 2 S cryodeposits, and recorded as a function of thickness and temperature from 88 K to evaporation points. Integrated band intensities were measured and are reported for all major absorptions. Assignments for lattice and internal fundamental modes are discussed. Particular attention is devoted to the various reported phases of solid NH 3 , and it is concluded that three phases are supported by experimental evidence: the stable cubic phase, a low temperature amorphous phase, and an intermediate temperature metastable phase. Results and changes of the spectra as a function of temperature will be summarized. Intercomparisons of the spectra obtained for the three cryodeposits are made.