The IR spectra of sevoflurane + acetone mixtures in liquefied Xe were studied at T ~ 165 – 190 K. Complex formation stabilized by noncovalent interactions of weak H-bond type has been identified on the basis of changes found at selected bands of both components. Quantum-chemical calculations made on MP2/6-311++G(d,p) level, show that the spectrum in the region of stretching vibrations of CH and CH2 groups is formed due to anharmonic effects, specifically Fermi resonances.

The sequences of Fermi resonances vs~2vb in the IR spectrum of a solution of fluoroform (CHF3) in liquefied krypton are investigated. Here vs is the CH stretching vibration, vb is the bending vibration. It is shown that for a correct description of resonance multiplets (polyads) at a high degree of vibrational excitation, it is necessary to use an extended set of spectroscopic parameters. In particular, it is necessary to take into account the dependence of the anharmonic interaction constant asbb on the vibrational quantum numbers. The conclusions are generalized for the arbitrary case of the CH-chromophore CHX3.

The IR absorption spectra of solutions of mixtures of halothane (C2HBrClF3) and trimethylamine ((CD3) 3N) in liquefied krypton were obtained and analyzed. Bands assigned to weak hydrogen-bonded complexes have been identified. The enthalpy of formation was estimated in a series of temperature experiments on the change in the integral intensities of the bands of monomers and complexes An extremely strong increase in the intensity of the second-order bands attributed to the first overtone of the bending CH vibrations of halothane was found. The effect is determined by strong anharmonic interactions of a resonant nature (Fermi resonance and Darling-Dennison resonance). The results of ab initio calculations reproduce the effects observed in the experiment.

A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH]+ linear complex along the profile of the proton transition reaction path is given, and the laws governing the diagnostic parameters, that is, potential descriptors of the dynamics of this process, are determined. We calculated the surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the reaction path of the proton transition in the system under study. When the fragments [HCNH]+ and NCH approach each other, a noticeable distortion of the forms of their skeletal vibrations occurs, up to complete mixing into the symmetric and antisymmetric forms. The frequency of the longitudinal vibration of the central proton ν(NH) varies along the reaction path from ~3600 to ~500 cm–1. An abrupt frequency change is observed in the region of intersection of the terms ν(NH) and ν(CN).

A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH] + linear complex along the proton transfer reaction profile is given, and the laws governing the diagnostic parameters — potential descriptors of the dynamics of this process — are established. The surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the proton transfer reaction path in the system studied are calculated. It has been shown that when the [HCNH] + and NCH fragments come closer together, a noticeable distortion of the forms of their skeletal vibrations occurs, up to complete mixing into the symmetric and antisymmetric forms. The frequency of the longitudinal vibration of the central proton ν (NH) varies along the reaction path from ~ 3600 to ~ 500 cm-1. In the region of intersection of the terms ν (NH) and ν (CN) an abrupt nature of frequency change is detected.

AbstractThe IR absorption spectra of subendothelial regions of the aortic valve cusps of a patient with calcified aortic stenosis diagnosis were measured by the attenuated total reflectance (ATR) spectroscopy technique in a frequency interval of 2500–3600 cm^–1 and analyzed in comparison to the spectra of healthy human tissues and reference spectra of a pig’s healthy bone and aortic valve. The IR absorption band structure in this spectral region was studied by means of expansion into Gaussian components. The energies of hydrogen bonds (H-bonds) involving O–H groups were estimated. It is established that, among all samples studied, the energy of H-bonds between hydroxyl groups reaches maximum in the bone tissue.

The IR absorption spectra of subendothelial regions of the aortic valve cusps of a patient with calcified aortic stenosis diagnosis were measured by the attenuated total reflectance (ATR) spectroscopy technique in a frequency interval of 2500–3600 cm –1 and analyzed in comparison to the spectra of healthy human tissues and reference spectra of a pig’s healthy bone and aortic valve. The IR absorption band structure in this spectral region was studied by means of expansion into Gaussian components. The energies of hydrogen bonds (H-bonds) involving O–H groups were estimated. It is established that, among all samples studied, the energy of H-bonds between hydroxyl groups reaches maximum in the bone tissue.

Vibrational relaxation is studied and the LR absorption spectra of CD3F in Xe, Kr, and Ar are obtained for the solid and liquid phases near the melting point. For CD3F in Xe and Kr, it was found that the rate of the process tau(-1) decreases and the main absorption bands of the CD3F molecule become broader on phase transition to the crystal state. For CD3F in Ar, the main absorption bands do not change their shapes and the quantity tau(-1) insignificantly increases its value on such a phase transition. The results obtained, together with results of gas-phase experiments, and the literature data for low-temperature matrices are discussed in terms of simple models of vibrational relaxation caused by isolated binary collisions (IBC) and collective interactions. At low temperatures, using the IBC model significantly underestimates the rate of vibrational relaxation in the solid phase. Within the framework of cell-like models, this fact can be connected with an increase in the relative efficiency of rotational channels of deactivation of the excitation energy because of the perturbation of orientational motion in more dense media.