Study on Photodissociation Dynamics of n-Pentyliodide Using Velocity Map Ion Imaging

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Photodissociation dynamics of n-C5H11I at 266 and 277 nm was investigated using velocity map ion imaging. Speed and angular distributions of the corresponding photofragments were obtained by detecting ion images of I*(5p(2)P(1/2)) and I (5p(2)P(3/2)). Quantum yields of I* and I were also obtained. The contribution of parallel and perpendicular transitions and the relative fraction of each potential surface at different excitation wavelengths were determined. These determinations were based on the relative quantum yield and the angular distribution. It is found that a very strong nonadiabatic coupling exists between the two excited states (3)Q(0) and (1)Q(1), and the curve crossing probability rises gradually with a decrease in the excitation wavelength. Additionally, analysis of the angular distributions for the I* channel and the I channel at the same excitation wavelength revealed that the population of (3)Q(0) was the main pathway following excitation. However, when compared to the situation that the I* channel mainly results from the direct dissociation of the (3)Q(0) state, the I channel originates mostly from the nonadiabatic coupling between (3)Q(0) and (1)Q(1).