Use of photoprocesses with charge transfer to excite active laser media

Abstract

A survey of various methods of optical excitation of ionic states, including excimer states, of molecules demonstrates the extensive potential optical pumping and makes it possible to determine the trends that are promising for further searches. Noticeable among them, firstly, is direct optical excitation and its accompanying secondary chemical processes with phototransport of electrons, which offer the researchers the largest choice of specific molecules and excitation mechanisms. We have shown, with molecular chlorine as the example, that the search for working media for optical pumping need not be limited to heavy molecules. The use of a complicated isotopic composition of molecules, Zeeman splitting of levels in a magnetic field, and impact broadening of spectral lines makes it possible to extend, within reasonable limits, the method of wide-band pumping to include also light molecules. As to secondary exchange reactions with charge transfer, in which optically excited molecules participate, it can be seen from the results of estimates of the cross sections that they constitute the largest class of excimerformation reactions and are characterized by additional possibilities of spectrally controlling the course of the reactions for the purpose of obtaining various products. Other promising methods considered here are production of ionic photodissociation states, including polar photodissociation, and also chemical radiative collisions. Note particularly the need for continuing the search for polyatomic excimers. It is obvious that production of such excimers is possible in media having a more complicated molecular composition, where such an advantage of optical pumping as the absence of induced absorption at the lasing wavelength is most strongly manifested.