Laser Excitation of Molecules to High States of Vibration

Abstract

High vibrational levels of molecules have gained interest in connection with some new concepts of isotope separation. Specific vibrational excitation of molecules is also of very basic interest to the reaction dynamicist who wishes to study the reactive behaviour of molecules prepared in a well-defined set of quantum states. It is the general context of laser chemistry at which the following report is primarily oriented. It reflects the early phase of a systematic study of the reactive behaviour of vibrationally excited molecules. Obviously these are old problems in the sense that the detailed energy dependence of chemical reaction rates has always been of central importance in our understanding of chemical processes. The new approach to these old problems is made promising by a new tool, the laser. This has indeed yielded some unexpected results. It is practical to distinguish from an experimental point of view work that has been done with single level excitation of low lying vibrational levels from distributed high level excitation. While the study of elementary chemical processes by specific excitation of low vibrational levels has been the subject of a number of papers within the last few years [1], the possibility to bring molecules into states of very high excitation has only opened up very recently. One method by which this can be accomplished is now termed “Infrared molecular superexcitation”.