The 5νNH and 5νND vibrational bands of partially deuterated ammonia species

Absorption spectra of gaseous samples containing NH2D and NHD2 have been measured in the 11 580-11 880 and 15 280-15 610 cm−1 regions, corresponding to the 5νND and 5νNH vibrational bands, respectively. Photoacoustic spectroscopy has been utilized for the measurement. The molecular constants of NH2D in the 5νND state and NHD2 in the 5νNH state have been determined from the analysis of the obtained absorption spectrum. From the comparison of the constants with those of the vibrational ground states, structural changes caused by the stretching excitations have been elucidated. The HND bond angles are decreased by these excitations. The dependence of the molecular constants on the stretching quantum number has also been derived by simple Birge-Sponer and Dunham analyses.