On the photodissociation of ozone in the range of 5-9 eV

The photoabsorption spectrum of ozone in the UV range (5-9 eV) is calculated from a short-time wave packet propagation using six potential energy surfaces obtained from ab initio electronic structure calculations. It is shown that the (unnamed) band around 7 eV, which is immediately adjacent to the intense Hartley band, is primarily due to excitation of three electronic states: 5 (1)A' (3 (1)A(t)), 6 (1)A' (4 (1)A(1)), and 4 (1)A (2 B-1(1)). Excitation of the state 8 (1)A' (B-1(2)) leads to a broad and intense band starting around 8 eV with a maximum near 9.1 eV. In full accord with the recent experimental study of Brouard et al. [M. Brouard, R. Cireasa, A.P. Clark, G.C. Groenenboom, G. Hancock, S.J. Horrocks, F. Quadrini, G.A.D. Ritchie, C. Valiance, J. Chem. Phys. 125 (2006) 133308], the excitation at 193 nm (6.42 eV) involves at least two states (5 (1)A' and 4 (1)A) different from the state excited in the Hartley band (3 W). The dynamics along the dissociation path is discussed in terms of one-dimensional potential curves. Several avoided crossings among the excited (1)A' as well as the (1)A states point to a complicated fragmentation process. Although a quantitative analysis of branching ratios is not possible on the basis of the present calculations, we surmise, that in addition to O(P-3) + O-2 ((3)Sigma(-)(g)) and 0(D-1) + O-2((1)Delta(g)), the next higher spin-allowed channel, O(D-1) + O-2((1)Sigma(+)(g)), also is likely to be a major product channel, in agreement with experimental observations. (C) 2007 Elsevier B.V. All rights reserved.