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 cryodepositsof methane and weak solutions of methane in nitrogen and argon in the temperature range from 12 K to 32 Kand at the deposition pressure of Р=10-4 Torr. The relation between the position of the absorption band ofdeformation vibrations ν4 and α-β phase transition in solid methane is established. Vibrational spectra ofcryodeposited mixtures of methane with argon and nitrogen obtained at various ratios of the componentsdemonstrate a correlation between the nitrogen or argon concentration and the absorption band ν4 position. Thepresence of 5% admixture of argon or nitrogen in the mixture leads to a violation of the reversibility of the α-βtransition. Although the initial heating of the sample from T=16 K to T=26 K clearly shows transition from theβ-phase to the α-phase at T=20 K, further heating and thermal cycling in the same temperature range results inthe spectrometer signal following a new trajectory, distant from the initial heating curve.