Vibrational C–H overtone spectroscopy and bond distances of butenes dissolved in liquid Xe

Vibrational overtone spectra of isobutene, cis-2-butene, and trans-2-butene dissolved in liquid xenon at 163 K, have been recorded between 5000 and 16500 cm−1. Spectral regions for the first four overtones were measured using a Fourier transform spectrophotometer. The fifth overtone (Δυ = 6) spectra were recorded with a double beam (pump–probe) thermal lens technique. Band deconvolution allowed isolation of individual transitions. Local-mode parameters were calculated for C–H oscillators in solution and compared with gas phase local-mode parameters. Density functional theory calculations were done to obtain C–H bond lengths and vibrational frequencies for the three butene isomers. Frequency shifts (Δω) with respect to gas phase results are attributed to changes in harmonic frequency and anharmonicity of the particular C–H bond of the sample dissolved in the inert liquid solvent.