Gas-phase photoacoustic overtone spectroscopy of ethylamine, ethylamine-N,N-d₂, ethyl-2,2,2-d₃-amine, and triethylamine

Intracavity dye laser photoacoustic spectra have been obtained for the v = 5 and 6 C-H stretching regions of ethylamine, ethylamine-N,N-d₂, and ethyl-2,2,2-d₃-amine. One methyl absorption and two methylene C-H absorptions were observed. The methylene peaks represent C-H bonds gauche to the nitrogen lone pair (higher frequency) and trans to the nitrogen lone pair (lower frequency). Two N-H peaks were observed and are assigned as the N-H trans to the methyl group (higher frequency) and the N-H gauche to the methyl group (lower frequency). Intracavity dye laser photoacoustic spectra have been obtained for the v = 5-7 C-H stretching region of triethylamine. Standard infrared techniques were used to obtain the fundamental and lower overtones (v = 1-4). Two peaks were observed in the overtone spectra for v ≥ 3 and were assigned as the methyl C-H stretch (high frequency) and the methylene C-H stretch (low frequency). The positions of both absorptions were fit to the local-mode model equation, and harmonic frequencies (ω_t) and anharmonicity constants (X_ii) are reported.