Konstantin S. Rutkowski

Temperature dependence of the νs(OH) band shape of ortho-Mannich bases in gas phase and liquid xenon solution

Abstract Infrared spectra of the two ortho-Mannich bases 2-( N , N -dimethylaminomethyl)-4-chlorophenol ( I ) and 2-( N , N -dimethylaminomethyl)-4,6-dichlorophenol ( II ) with a medium-strong intramolecular hydrogen bond, were measured in a wide frequency (4000-50 cm −1 ) and temperature (−105°C to +120°C) range in liquid Xe, CCl 4 solutions and gas phase. The temperature studies of the first and second spectral moments of the ν s (OH) band in liquid Xe within the temperature range from −105 to +30°C allow for the analysis of the ν s (OH) mode coupled with the low-frequency vibrations (ν l ) of the non-linear hydrogen bond. Transitions located at ca. 150, 250 and 340 cm −1 were selected as such ν l modes. The effective coupling parameter between high-frequency ν s (OH) and low-frequency ν l vibrations of the hydrogen bridge was evaluated: b = α ssl /ω l ⋍ 0.7. Model calculations accounting for the hot and combination transitions give satisfactory reproduction of the gas phase ν s (OH) and ν s (OD) bands shapes. Both temperature experiments and model calculations predict that even at 0 K the halfwidth of the ν s (OH) band can be quite large, viz. ca. 200–400 cm −1 .

Effect of liquid to solid phase transition on rotational and vibrational broadening of vibrational bands of CF3CL in Xe solutions

Abstract Fundamental and second order bands of CF 3 Cl dissolved in Xe solutions have been studied near the melting point by using technique of transparent solid sample growth from the liquid rare gas solution. The widths at half maximum 2 Γ of the bands were noticeably decreased after crystallization, especially in the case of the broadest 2 ν 4 ( E ) band. Experimental data have been interpreted in the framework of Debye limit (〈 ω 〉 τ J ≪1) for the J -model of a heavy symmetrical top rotation. Additional broadening, caused by fluctuational mechanisms of vibrational relaxation, was taken into account. Angular momentum correlation times ( τ J ⊥ and τ J ∥ ) and parts of widths, originated from vibrational relaxation, were estimated for the liquid and solid Xe solutions near the melting point. The results obtained have shown decreasing effect of fluctuational broadening and increasing disturbance of rotational motion of CF 3 Cl when going from the liquid Xe solution to the crystal state.

Degeneracy Lifting Effect in the FTIR Spectrum of Fluoroform Trapped in a Nitrogen Matrix. An Experimental and Car-Parrinello Molecular Dynamics Study.

The FTIR spectra of fluoroform trapped in argon and nitrogen matrixes are studied at T ∼ 10-30 K. The bands of E symmetry show the splitting effect in a nitrogen matrix, which is absent in an argon matrix. The effect is the most prominent in the case of the ν4 CH bending vibration. It decreases slightly with increasing temperature. Both static and Car-Parrinello molecular dynamic simulations suggest that the degeneracy lifting is due to C3v symmetry lowering caused by interactions between fluoroform and all neighbor N2 matrix molecules.