Molecular reorientation in liquid acetonitrile studied by depolarized light scattering experiments

Abstract

Time correlation functions from depolarized light scattering experiments at several temperatures were examined by biexponentials that simultaneously account for the unique axis molecular reorientations (on the picosecond time scale) and collisional processes (on the subpicosecond time-scale). The first are found to be systematically slower than those obtained in previous studies. The important role played by dipolar interactions on the molecular organization in the liquid is confirmed. Comparison with dielectric relaxation times indicates that rotational diffusion provides only an approximate description of molecdar reorientation in liquid acetonitrile. Application of the Jdiffusion model shows that the exponential decay of the observed orientational correlation fnnctions cannot be taken as evidence of rotational diffusion in liquid acetonitrile.

IRMPD Spectroscopy of a Protonated, Phosphorylated Dipeptide

“…It is of great interest to study collective vibrational and rotational motions in liquids using Raman spectroscopy. The study provides an insight into the structure and the dynamic processes taking place in liquids 1–9. Vibrational Raman bandshapes observed in the spontaneous Raman scattering process are broadened by homogeneous and inhomogeneous line‐broadening mechanisms.…”

“…The two mechanisms contributing to the vibrational bandshape, such as the vibrational and the reorientational relaxations, can be studied separately using the Raman spectroscopic technique. During the past several years, vibrational relaxation and molecular reorientational processes in liquids have been studied by analyzing1–27 the bandshape of the isotropic ( I iso ) and anisotropic ( I aniso ) components of the Raman band of the molecule. A variety of theoretical models has been proposed to describe the influence of a solvent on vibrational wavenumbers and bandwidths.…”

“…It was found that the bandshape in the neat liquid approaches the Lorentzian shape. Therefore, the time correlation function provides dynamic information about a variety of molecular liquids with respect to the molecular reorientation and vibrational relaxation in molecules 5–9…”

Tumbling and spinning diffusions of acetonitrile in water and organic solvents

“…The rotational motions of acetonitrile have been investigated by various methods: IR, [7][8][9][10] Raman, [9][10][11][12][13][14] dynamic light scattering, [12][13][14][15] NMR, 6,[16][17][18][19][20][21][22][23][24][25] pulse laser, [26][27][28] and computer simulation. 23,24,[29][30][31] Most of the studies are, however, confined to neat liquid or in rather concentrated solutions.…”

Relaxational Molecular Motions in Simple Organic Liquids: Studies with Low-Wavenumber Depolarized Raman Spectroscopy

“…Recently, Giorgini et al 23 reported the relaxation time in acetonitrile obtained with another method which also takes account of the existence of the higher wavenumber components. They obtained the relaxation time by Ðtting the time-correlation function which was the Fourier transform of the depolarized Rayleigh spectrum.…”