FIG. 4.

Determination of the reaction pathways of I₃^– photodissociation in methanol with ((a), (b)) 400 nm and ((c), (d)) 267 nm laser excitations in ((a), (c)) q-space and ((b), (d)) r-space. (a) Theoretical difference scattering curve (red) for each candidate pathway is shown together with the experimental difference scattering curve at 100 ps (black). The model employing only the two-body dissociation pathway gives much better fit than the models employing the three-body dissociation and I₂ formation pathways, indicating that two-body dissociation is the dominant reaction pathway with 400 nm laser excitation. (b) Radial distribution functions, rΔS(r,t), of solute-only term. Bond distances and their contributions of various I–I pairs are indicated as red bars and dashed curves, respectively, at the top. With the model employing only two-body dissociation, the experimental and theoretical RDFs of solute-only term are in good agreement. (c) The same analysis of (a) for 267 nm laser excitation. The models employing the two-body and three-body dissociation pathways give similarly good fitting qualities, indicating the possibility of multiple reaction pathways. The best fit was obtained with a model employing all three reaction pathways. The optimum ratio of the contributions of two-body and three-body dissociation was determined to be 7:3. (d) The same analysis of (b) for 267 nm laser excitation. With the model employing the two-body and three-body dissociation pathways with the branching ratio of 7:3, the experimental and theoretical PDFs of solute-only terms are in good agreement.