Leo J. Laux

A charge flow model for vibrational rotational strengths

The valence‐optical approach is used to construct a model applicable for the calculation of rotational strengths associated with fundamentals of vibrational transitions. It is shown that the model has the essential property of giving rotational strengths that are independent of the choice of origin.

Some theoretical considerations for magnetic vibrational circular dichroism spectra

Expressions are derived for the A terms, B terms, and associated partial anisotropy factors relevant for the magnetic vibrational circular dichroism (MVCD) spectra of molecules with nondegenerated ground states. These expressions are derived subject to the approximations of the harmonic fixed partial charge model and the condition of magnetic coupling among only the ground electronic state vibrational levels. Numerical values for partial anisotropy factors calculated from these expressions, when taken in conjunction with the recent MVCD data of Keiderling, suggest the importance of magnetic coupling of the ground electronic state with higher electronic states in the case of B terms. Symmetry constraints on the nonvanishing of such coupling terms also suggest the possible utility of MVCD data for providing spectroscopic and molecular structural information.

The Determination of Absolute Infrared Intensities with a Fourier Transform Spectrometer

In principle it is apparent that Fourier transform infrared spectroscopy offers a number of significant advantages in the determination of infrared intensities integrated over the rotational fine structure in vibration-rotation bands. One expects that there should be no problem with photometric accuracy; yet, before embarking on a systematic program of study, we believe it important to establish that the method will work in practice. As a test case we have chosen the V2 fundamental of CO2 at 673 cm−1 since this is, in our experience, as difficult a band as any when it comes to measuring integrated intensities. We have, using a Digilab FTS-20 spectrometer, determined a value of the integrated intensity, Γ2 = 7901 ± 105 cm2/mol which should be compared with the value previously determined on a dispersive instrument, Γ2 = 7882 ± 110 cm2/mol. We have also determined a value of Γ3 = 25,300 ± 570 cm2/mol for the integrated intensity of the antisymmetric stretching fundamental.

The charge flow model applied to the vibrational circular dichroism of oriented species

Abstract The charge flow model is applied to the vibrational circular dichroism associated with oriented species. Expressions are derived for the three rotational strengths associated with light propagating along three orthogonal axes. The relevance of these expressions for the determination of the vibrational electric quadrupole transition moment is discussed.