ANALYSIS OF IR ABSORPTION-SPECTRUM OF O-3 IN INERT MATRICES - SPECTROSCOPIC EVIDENCE FOR 2 TRAPPING SITES

The infrared spectra of solid O3 and of O3 trapped in rare gas and nitrogen matrices are analyzed, mainly with O-16(3), a few experiments being performed with O-18-substituted species. The nu3 mode appears as a doublet except in solid nitrogen. The intensity ratio between the two components is dependent upon the deposition temperature. This gives evidence for two trapping sites. In the nu2 region, the spectrum exhibits a narrow line and a structure of two weaker lines which can be assigned to monomeric O3. The two nu3 components show a very different temperature dependence: one broadens as soon as 15 K, while the effect is significant for the second one only at 25 K. The different hypotheses for the trapping sites are discussed, and the reversible temperature broadening of the nu3 lines is tentatively explained through a phonon-assisted vibrational energy transfer from the nu3 mode to the lowest one nu2.