P.-A. Lund

Comparison of depolarized rayleigh-wing scattering and far-infrared absorption in molecular liquids

Abstract The absorbed energy in a depolarized Rayleigh-wing scattering experiment is constructed from the measured intensity and compared with the far-infrared

Intermolecular Raman active vibrations of hydrogen bonded acetic acid dimers in the liquid state

Low frequency Raman spectra (20–250 cm−1) of liquid CH3COOH, CH3COOD, and CD3COOD at room temperature were studied. The experimental data were directly transformed to the R(ν) representation, previously described. The three Raman active intermolecular vibrations of the cyclic dimer (C2h symmetry) were assigned by use of depolarization ratios and a comparison of vibrational frequencies for the different isotopic molecules.

Low-frequency Raman spectra of liquid formamides and aqueous solutions of formamide

Abstract Low-frequency Raman scattering of liquid formamide, aqueous solutions of formamide, liquid N-methylformamide and N,N-dimethylformamide are studied by construction of a quantity R ( V ). Previous experimental observations (far-infrared and Raman) in this frequency region are compared to those obtained from the R( v ) representation.

Comments on the R(ν̄) spectral representation of the low frequency Raman spectrum

A few misunderstandings concerning our use of the R (?) spectral representation are clarified. Two different spectral representations for the low frequency Raman spectrum are compared.

Aspects of low frequency vibrations (20–350 cm−1) from Watson-Crick base pairing in an aqueous solution of tRNA

Summary The low frequency Raman spectrum from 20 cm −1 to 350 cm −1 of tRNA from Escherichia coli in an aqueous solution is studied. A band at ca . 115 cm −1 is assigned to displacements of atoms in hydrogen bonds between Watson-Crick base pairs. Temperature studies between room temperature and ca. 90°C are performed showing near reversibility of the base pairing upon temperature. The couplings between low frequency vibrations of tRNA and formamide, N-methylformamide and N,N-dimethylformamide are discussed in terms of physiological effects.

Low-frequency Raman spectra of fluorobenzene in the liquid state

Abstract Low-frequency Raman spectra of liquid fluorobenzene at −15°C and 60°C are investigated. Both spectra show in the R( ν )-representation a broad band with a maximum at approximately 75 cm−1. This is assigned to librational motions. A simple model based on a damped oscillator is used to explain main features in the spectra.

Studies of the reorientational relaxation of pyridine in water by depolarized Rayleigh light scattering

The depolarized Rayleigh spectra of aqueous solutions of pyridine have been studied using a high‐finesse Fabry–Perot interferometer as a function of temperature and concentration. The Rayleigh relaxation times are found to have a complex concentration and viscosity dependence. The classical Stokes–Einstein–Debye equation for molecular reorientation breaks down in this system. The Rayleigh relaxation time of pyridine molecules is not determined by the macroscopic shear viscosity of the solution. The specific interaction due to the formation of hydrogen bonds between pyridine and water molecules plays a very important role in affecting the relaxation time. At a fixed temperature the plot of πray/η versus pyridine concentration shows two maxima at low and high pyridine concentrations. The low concentration maximum is due to the incorporation of pyridine molecules in the water network structure and the high concentration maximum is associated with the formation of individual pyridine–water complexes. The acti...

Light scattering from orientational and density fluctuations in liquid 1,2,5‐thiadiazole

The orientational and density fluctuation spectra of liquid 1,2,5‐thiadiazole were determined by the light scattering technique. The viscosity and density of the pure liquid were also measured as a function of temperature. Results of concentration dependent studies of 1,2,5‐thiadiazole in an optically isotropic solvent having the same viscosity as the pure liquid show that the pair orientational correlation is very small. The experimentally determined reorientational relaxation times were found to be close to the prediction of the slip model for rotational diffusion. The sound velocity of the pure liquid was found to decrease linearly with increasing temperature. The sound dispersion was found negligible in the GHz frequency region.