Features of relaxation processes in methane cryocondensates and weak methane solutions in nitrogen and argon

Abstract

The paper presents results of IR-spectrometric studies of phase transition peculiarities in thin-film cryodeposits of methane and weak solutions of methane in nitrogen and argon in the temperature range from 12 K to 32 K and at the deposition pressure of Р=10-4 Torr. The relation between the position of the absorption band of deformation vibrations ν4 and α-β phase transition in solid methane is established. Vibrational spectra of cryodeposited mixtures of methane with argon and nitrogen obtained at various ratios of the components demonstrate a correlation between the nitrogen or argon concentration and the absorption band ν4 position. The presence of 5% admixture of argon or nitrogen in the mixture leads to a violation of the reversibility of the α-β transition. Although the initial heating of the sample from T=16 K to T=26 K clearly shows transition from the β-phase to the α-phase at T=20 K, further heating and thermal cycling in the same temperature range results in the spectrometer signal following a new trajectory, distant from the initial heating curve.