ELEMENTARY PROCESSES IN THE DECOMPOSITION OF OZONE

Potential-energy surfaces are considered for the 04 complex, treated as the three-body complex 0 . . . 0 . . . 02. By means of these it is shown that 0(3P) reacting with O3 may give rise to a molecule of 02 in its gro~~~ld state and one in any of the states 32,- (ground), 'A,, and 'Z,+; %,,+ cannot be produced. Most of the oxygen molecules produced are expected to be in the ground electronic state, but will be vibrationally excited. Such molecules are readily deactivated and unlilcely to lead to energy chains by the reaction 02* + 03 -) 202 + 0. Such chains are therefore unlikely in the thermal deco~nposition and in that initiated by visible radiation. In ultraviolet light O('D) atoms are produced and the potential-energy surfaces show that these give rise very efficiently to O('D) + 03 + 02 + 0?(3Zu-); the latter have 141 kcal in excess of the gro~~nd state. It is suggested that the subsequent radiative process is responsible for sustaining the population of vibrationally excited oxygen molecules in the ground state and that these propagate energy chains, as postulated by McGrath and Norrish (I).. The significance of these concl~~sions is discussed with reference to the experimental evidence.