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Vibrational relaxation time measurements in CH4 and CH4-rare gas mixtures

1977; Elsevier BV; Volume: 86; Issue: 3 Linguagem: Inglês

10.1016/0378-4371(77)90091-7

1873-2119

MJS Vasconcelos, A.E. De Vries,

Molecular Spectroscopy and Structure

Abstract With a spectrophone vibrational relaxation times in CH4 and in mixtures of CH4 with rare gases were measured. Both the amplitude and the phase method were used. The two infrared active modes of CH4 (ν4 and ν3) were investigated separately. The relaxation times, at one atmosphere, after exciting the lowest mode ν4, were found to be: τ(CH4-CH4) = 1.65 μs; τ(CH4-He) = 1.97 μs; τ(CH4-Ne) = 8.6 μs; τ(CH4-Ar) = 12 μs and τ(CH4-Kr) ≈ 60 μs. From these values one may in that vibrational-rotational (V-R) energy transfer is the dominant relaxation mechanics. By exciting the higher mode the first step in the deactivation of ν3 was found to be a V-V transfer to the lowest modes ν4, ν2.