INTERPRETATION OF THE INFRARED-SPECTRUM OF OZONE TRAPPED IN INERT MATRICES

The infrared spectrum of O3 trapped in rare ps crystals is interpreted on the basis of two trapping sites, the single and double substitutio nal sites in which the molecule experiences nearly the same total ener gy, but its orientational motions are different. In the single cage, t he direction of the larger dimension of the molecule librates about th e C4 axis of the site, which is the only restriction to the proper rot ation; in the double cage, the only motions are librational. The model then explains the occurrence at low temperature, for the nu3 mode in both sites, of one sharp signal corresponding to a Q line, whereas the nu2 mode appears as a weak hindered rotational structure in the singl e site and as a single sharp Q line in the double site. Calculations a re furthermore performed to determine the width of the nu2 and nu3 pea ks and to analyze the various processes responsible for the different behavior of the broadening of the two nu3 signals as temperature rises . It is shown that one- and two-phonon inelastic collisional processes contribute in a different way to the broadening mechanism of the nu3 peak profiles.