EXPERIMENTAL-STUDY OF THE CO-O-3 COMPLEX IN ARGON MATRICES - IRRADIATION AT 266-NM

Codeposition of argon dilute samples of O-3 and CO produced new narrow absorption lines which are assigned to the CO:O-3 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 v(3) doublet of O-3. 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 v(3) doublet of isolate O-3 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 O-3 and CO:O-3 decay followed by a much slower one. After such an irradiation at 5 K, some recombination of O-3 and CO:O-3 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:O-3 complex, from the reaction of CO with D-1 atomic oxygen. As D-1 oxygen atoms are very fastly relaxed to P-3 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.