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Low-temperature infrared absorption spectra are obtained for ethanol isolated in an argon matrix at temperatures of 20-45 K range for ratios of the numbers of the molecules being studied to the numbers of matrix atoms of 1:1000 and 1:2000. A preliminary interpretation of the spectra is obtained on the basis of the temperature variations in the spectra and published data. The structure of the ethanol conformers, rotational constants, and internal rotation barriers of the methyl and hydroxyl groups are calculated in the B3LYP/cc-pVQZ approximation. The harmonic and anharmonic IR spectra of the gauche- and trans-conformers are calculated in the same approximation. The force fields of the two conformers and the distributions of the potential energy of the normal vibrations are calculated and compared for a general set of dependent coordinates. Anharmonicity effects are taken into account by introducing spectroscopic masses for the hydrogen atoms when calculating the normal vibrations in the harmonic approximation. [ABSTRACT FROM AUTHOR]

Intermolecular hydrogen bonding, which is formed between water molecules in the condensed state, causes a variety of unique properties of liquid water. In this paper the results of experimental FT IR studies of water trapped in an Ar matrix as well as condensed water at temperatures from 133 to 293 K are presented. It is shown that the temperature evolution of the FTIR-spectra of water trapped in low-temperature matrices can be considered as an experimental model of the structure transformation of water during the phase transition from gas phase to condensed confined water. The comparison of the vibrational spectra of water in matrix isolation with the corresponding spectra of condensed water gives information about the peculiarities of H-bonded structures of water. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two conformers of PyO⋅TCA complex in acetonitrile with short hydrogen bond were found. [•] For conformers IR spectra were calculated in harmonic and anharmonic approximations. [•] 1–3D PES for the motion of the hydrogen atom in both conformers were build. [•] Frequencies of OH vibrations were found by numerical solution of Schrödinger equation. [•] We analyzed increasing of anharmonicity while solving PyO⋅TCA complex in acetonitrile. [ABSTRACT FROM AUTHOR]