Determination of anharmonicity constants from the Raman spectrum of gaseous acetylene

From an analysis of the photoelectrically recorded Raman band of acetylene at 3950 cm−1, which contains contributions from ν1+ν4 and its hot bands, ν3+ν5 in Fermi resonance with ν2+ν4+2ν5, and the Q‐branch of 2ν2, some anharmonicity constants were determined. In particular x22= −7.4 cm−1 was obtained directly for the first time, other constants are revised due to a more complete consideration of the resonance perturbations. A computer simulation of the ν4 fundamental and the ν1+ν4 combination band shows excellent agreement with the experimental spectra.