Shape of the IR bands of CH4: The CH4-Kr system in different phase states

The IR absorption spectrum of mixtures of CH4 with Kr in the range 800-6000 cm(-1) is studied in the region of the gas-liquid and liquid-crystal phase transitions. It is found that, as the system density increases, the ratio of the v(4) band intensity to that of the v(3) band becomes larger and the measured values of the second spectral moment of the v(4) band become small er than the corresponding calculated values. The quantum counterpart of the generalized J-diffusion model was used to describe the shape of the v(3) a nd v(4) bands, and the rotational relaxation times of CH4 in solutions were obtained. It was shown that, as the density increases, a broad 1470-cm(-1) band appears in the region of the "forbidden" (induced by a Coriolis inter action) v(2) band (v(Q) = 1535 cm(-1)) detected in a low-density gas. The i ntensity of this band is appreciably higher than that of the v(2) band. (C) 2000 MAIK "Nauka/Interperiodica".