Chain Reaction Mechanism for I2 Dissociation in the O2 (1 delta)-I Atom Laser.

Abstract : A chain reaction model for I2 dissociation in O2* is proposed. Experiments in a computer-controlled flow tube apparatus indicate that I2 (X) dissociation is initiated by collisions with O2(1 sigma); subsequently, the I atoms formed are pumped to I* by O2(1delta). Other initiation mechanisms are also discussed. Chain branching occurs when I* transfer energy to I2(X) to form I2 and I2 is dissociated into I atoms by collisions with O2(1 delta). Chain termination in these experiments is caused by I-atom wall recombination. An analytic model is presented that favors the above explanation over several others that are kinetically similar. Numerical modeling calculations are included to verify this simplified model. Scaling relationships are developed for I2(X) dissociation as a function of O2(1 delta), O2(3 sigma), I2O, H2O, and Ar. The I2 intermediate (I2 ) is not directly observed; however, indirect evidence indicates that it is vibrationally excited I2(X).