AXIS-SWITCHING
Loading...
Date
1964
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Complications arise in the calculation of the intensities of rotational and vibrational transitions accompanying an electronic transition because the coordinates in terms of which the rovibronic wave functions are most conveniently expressed are not in general identical for the two electronic states. These latter coordinates are ordinarily defined in conjunction with a coordinate axis system which in some sense translates and rotates with the molecule. The orientation in space of this moving set of coordinate axes depends not only upon the instantaneous positions of the atoms of the molecule, but also upon the equilibrium configuration from which the atoms are regarded as being displaced. When discussing an electronic transition of the molecule, two equilibrium configurations, which are in general different, and so two sets of moving axes, must be considered. These axes have coincident origins, but in general one set is rotated with respect to the other. The convenient set of axes to use changes abruptly during the electronic transition. This changeover from one axis system to the other will be called ``axis-switching''. Although axis-switching apparently arises in a rather formal way, there are observable physical effects associated with it. These consist essentially of a breakdown, in certain electronic transitions, of the ``normal'' intensity rules, which have been derived for vibration-rotation spectra, where only one equilibrium configuration need be considered.
Description
Author Institution: Division of Pure Physics, National Research Council