Effect of chemical substitution on absorption spectra and magnetic circular dichroism of molecules in dense media

The purpose of this paper has been to study the effect of chemical substitution on the magnetic circular dichroism and absorption spectra for the parent molecule which has the C(2v) symmetry. Four electronic transitions, A(1) --> A(1), A(1) --> B(1), A(1) --> B(2), and A(1) --> A(2) have been considered. In each case, the intensity changes in magnetic circular dichroism and absorption spectra due to substitution have been expressed in terms of number of substituents and positions of substitution.

Magnetic circular dichroism of molecules in dense media: benzene

This paper presents some calculated results on the vibrational structuring of the magnetic circular dichroism of the benzene (1)A(1g)"(1)B(2u) transition. The good agreement between the experimental and calculated relative intensities of the B-bands (positive magnetic circular dichroism bands) indicates that these bands are mainly induced by the e(2g) 1596 cm(-1) mode. The unfavorable results obtained by comparison of the theoretical results with experimental results for the A-bands (negative magnetic circular dichroism bands) is presumably due to neglect of the contribution from the e(2g) 3056 cm(-1) mode, from hot bands, and from the transitions of normal modes other than the A(1g) 992 cm(-1) mode. It should be noticed that while the e(2g) 608 cm(-1) mode plays a dominating role in the ultraviolet spectrum of benzene, in the magnetic circular dichroism of benzene, the e(2g) 1596 cm(-1) mode is, if not more important, at least as important as the e(2g) 608 cm(-1) mode.

Theoretical analysis of emission spectra of electronic transitions of molecules in dense media

The purpose of this paper is to investigate the nature of band shapes of emission spectra and their relation to the rate of nonradiative processes. Two cases are discussed, one in which the Franck-Condon principle applies and the other in which the electronic transition is symmetry-forbidden but vibronic-allowed. The moment relations of emission spectra have been derived and their applications demonstrated.The vibrational structuring in emission spectra is discussed and empirical equations for calculation of the shapes of vibrational bands are derived. It is found that from the shapes of vibrational bands one can obtain the information of intermolecular vibration and from the areas under vibrational bands one can determine the Franck-Condon factors of intramolecular vibration.

Kinetics of heterogeneous chemical reactions: a theoretical model for the accumulation of pesticides in soil

A theoretical model for the accumulation of pesticides in soil has been proposed and discussed from the viewpoint of heterogeneous reaction kinetics with a basic aim to understand the complex nature of soil processes relating to the environmental pollution. In the bulk of soil, the pesticide disappears by diffusion and a chemical reaction; the rate processes considered on the surface of soil are diffusion, chemical reaction, vaporization, and regular pesticide application. The differential equations involved have been solved analytically by the Laplace-transform method.

Calculation of the reaction cross section from a rate constant by the method of steepest-descent

The reaction cross section of a bimolecular reaction has been calculated from the corresponding rate constant by the inverse Laplace transform. In carrying out the inverse Laplace transform, the method of steepest-descent has been used. As applications, the reaction cross sections for the rate constant of k(T) = k' T(n)e(-E0/kT) and for the rate constant of the absolute reaction rate theory have been calculated. The computation of the energy density function associated with the definition of the weighted-average cross section has also been discussed.

Kinetics of heterogeneous chemical reactions. II

The first-order and zero-order kinetics of heterogeneous reactions coupled with the diffusion process are studied. The differential equations of these reaction systems are solved for the cases in which the fluid is not stirred and the fluid is well stirred. It is shown that both the rate constants and the diffusion coefficient can be determined in various ways depending on the experimental conditions.