Multi-pathway I2 dissociation model for coil

Vibrationally excited iodine I-2(X,v>20) is an important intermediate in the standard COIL dissociation model. This intermediate is populated by the I* + I-2(X) reaction. In this model excitation probabilities for the v-th I-2(X) vibrational level gamma(v) are critical parameters. In the present study we examined excitation probabilities gamma(v) based on the comparison of calculated populations of vibrational levels of iodine molecules with their experimental values. The total excitation probability for I-2(X v>25) was found to be gamma(v>25)approximate to 0.1. The standard dissociation model with gamma(v>25)approximate to 0.1 cannot provide the observed dissociation rates. Moreover the number of O-2(a) molecules consumed per dissociated 12 molecule would exceed 20 if the standard dissociation model is the predominant dissociation pathway, which is at variance with experiment. Barnault et al.(3) found that the populations of I-2(10 <= v <= 23) were much higher than upsilon >= 30. Such high populations of I-2(10 <= v <= 23) could be explained by means of direct excitation in the I* + I-2(X) reaction. A satisfactory agreement between calculated I-2(V) populations and the experimental data was achieved for the total excitation probability gamma(v>25) =0.05-0.1 and for gamma(15<v<25) =0.8-0.9. In this work a multi-pathway dissociation model is developed. The I-2 dissociation pathway where electronically excited states I-2(A', A) serve as intermediates is dominant. These states are populated by the reactions: O-2(a,v=1) + I-2(X) -> O-2 (X) + I-2(A') O-2(a,v=1) + I-2(X) <-> O-2 (X) + I-2(A') I-2(X,10<v<25) + O-2(a) -> O-2(X) + I-2(A',A). The results of computer calculations utilizing the multi pathway model are in good agreement with experimental iodine dissociation rates.