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The recently reported fluorescence, emitted near 10 μm by laser excited ozone molecules trapped in xenon matrices, is actually a stimulated emission. It is observed, at the 2ν3→ν3 frequency, only if the laser pulse, which excites the ν1+ν3 level, contains a sufficient amount of energy. A similar emission is found in the other rare gas matrices and in nitrogen, above a laser energy threshold which is matrix dependent. Above the threshold, the emitted signal grows linearly with the laser pulse energy. An evaluation of the quantum yield is obtained by comparison with the literature data on CO fluorescence. The characteristics of the observed emission (low directionality, laser energy dependence, shortening, and amplification when compared to spontaneous emission) are discussed.

Codeposition of argon dilute samples of O3 and CO produced new narrow absorption lines which are assigned to the CO:O3 complex. One line appears at 2140.44 cm−1, 2 cm−1 above the CO frequency which shows that it is a weakly bonded complex. Its spectrum exhibits three new lines near the ν3 doublet of O3. The two lines observed at 1042.56 and 1043.37 cm−1 appear clearly at 5 K; the lowest frequency one, at 1041.35 cm−1, is overlapped at 5 K by the high frequency component of the ν3 doublet of isolated O3 and can only be detected when the temperature is raised, as it is almost not temperature dependent up to 20 K. Irradiation of the sample at 5 K with the 266 nm emission of a quadrupled ND-YAG laser leads to an efficient decomposition of free and complexed ozone and an increase of CO2 with two regimes, a fast beginning similar to the O3 and CO:O3 decays followed by a much slower one. After such an irradiation at 5 K, some recombination of O3 and CO:O3 is observed during a warming at 10 K. A careful analysis of the relative intensities variation shows that CO2 is only produced inside the CO:O3 complex, from the reaction of CO with 1D atomic oxygen. As 1D oxygen atoms are very fastly relaxed to 3P ones during their migration through the matrix, isolated CO does not react. We have shown evidence of a very limited migration of atomic oxygen at 5 K in solid argon, and of an efficient one at 10 K.

The CO:CO2 complex in argon matrices is identified near the CO absorption which appears at 2138.49 cm−1, slightly shifted from the pure argon value of 2138.64 cm−1, because of the presence of CO2. It exhibits two features on each side of the CO frequency: a doublet at 2143.34 and 2143.01 cm−1 (HF A and B lines) and a narrow line at 2135.38 cm−1 (LF line); these small shifts indicate weakly complexed C–O stretching modes. When the temperature is raised from 5 to 12 K, the LF line decreases progressively and disappears at the benefit of the HF A and B lines, the total absorption intensity remaining unchanged. This effect is perfectly reversible and can be explained by an exchange between two different conformations of the CO:CO2 complex, with complexed C–O bonding shifted either towards a higher frequency (HF form), or towards a lower one (LF form). Furthermore, after a fast cooling down to any given temperature below 12 K, the intensity ratio between the two forms is time dependent; the high temperature form (HF form) converts into the LF form within a few minutes. The equilibrium value of the intensity ratio LF/HF and the rate constants for the conversion are temperature dependent. We have checked that this conversion, occurring without any temperature change, is not photoinduced.