The fate of primary ozonides and carbonyl oxides arising from the ozonolysis of isoprene is investigated using a statistical-dynamical master equation and transition state theory. Excited carbonyl oxides are shown to dissociate promptly to produce OH (11%) or isomerize to form dioxirane (32%). while the remaining (57%) are collisionally stabilized. An OH formation yield of 0.25 from prompt (0.11) and thermal (0.14) decomposition of the carbonyl oxide is obtained. The results reveal slow thermal decomposition of the carbonyl oxide to form OH. For formaldehyde. MACR, and MVK, the yields are estimated to be 0.67, 0.21, and 0.12. respectively. (C) 2002 Elsevier Science B.V. All rights reserved.