Depolarized Rayleigh scattering and orientational relaxation of molecules in solution. II Chloroform and nitrobenzene

Abstract

Measurements of orientational relaxation times of chloroform and nitrobenzene in a variety of solvents have been made by depolarized light scattering. At constant concentration a plot of reorientational relaxation time of nitrobenzene versus solution viscosity was found to fit a straight line with nonzero intercept. The reorientational relaxation time of both solutes increased with increasing solute concentration (at constant viscosity). For nitrobenzene and chloroform, plots of the reorientational relaxation time versus solute concentration were linear. This concentration dependence is attributed predominantly to pair correlations. The ``static'' correlation parameter f and the ``dynamic'' correlation parameter g are determined for both chloroform and nitrobenzene. The carbon-13 spin-lattice relaxation time (T1) for both solutes in solution has also been determined. The reorientational relaxation time of chloroform determined by NMR agrees well with the reorientational relaxation time determined by depolarized light scattering extrapolated to zero solute concentration.

Excited-State Dynamics of Donor−Acceptor Bridged Systems Containing a Boron−Dipyrromethene Chromophore: Interplay between Charge Separation and Reorientational Motion

“…Similar measurements have been performed in other solvents of various viscosities, and the resulting anisotropy decay times are listed in Table 3. Figure 7 indicates that τ r increases linearly with viscosity, in agreement with the following modified Stokes-Einstein-Debye equation: 62,63 where τ r0 is the zero-viscosity intercept, k B is the Boltzmann constant, T is the temperature, and f is a shape factor that depends on the axis ratio of the ellipsoid. For TMBDY, which can be considered as a prolate ellipsoid with an axis ratio of 1.5 and with the transition dipole moment oriented along the long axis, f can be estimated to be around 1.2.…”

The Dynamics of Benzene Molecules in Liquid Carbon Tetrachloride Solution

“…3. This dependence, which is in accordance with the measurements of Alms et al [8] evidences the increase of benzene self-association with the decrease of its concentration.…”

Theory of molecular reorientation rates, flow birefringence, and depolarized light scattering

“…it may possibly be associated with inertial motion [20] of the molecules, but for some systems it appears to be very small, zero or even negative [21]. More work is necessary to understand this quantity, f is defined as [7] oo…”