Infrared Spectra of Ammonia Suspended in Solid Nitrogen

Abstract

Matrix isolation studies of the infrared spectra of ammonia suspended in solid nitrogen at 20°K are presented. Variation of the mole ratio of nitrogen to ammonia shows that monomeric NH₃ in solid nitrogen absorbs at 3440, 3332, 1620–1632, 1143, and 970 cm^—1. A large enhancement of ν₃, 3440 cm^—1, occurs relative to ν₁, 3332 cm^—1, just as observed for the pure solid. The totally symmetric vibrations ν₁ and ν₂ are relatively sharp (half‐widths are 1 and 1.5 cm^—1, respectively). The umbrella mode ν₂ shows no evidence of inversion nor of free rotation. The band at 1143 cm^—1 is ascribed to ν₂ in combination with librational movement about the B axes. The constraints to movement within the nitrogen matrix cage seem to be larger than those reported for inert‐gas matrices. Some results on the hydrogen bonding in dimeric and polymeric ammonia are reported. The dimer absorbs at 3404, 1004.5, 987 cm^—1 and possibly as well at 3313, 3246 and 3237 cm^—1.