Nanosecond and femtosecond probing of the dynamics of the UV-photodissociation of perfluoroethyliodide C2F5I
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The ns photodissociation of perfluoroethyliodide C2F5I at 266 nm has been studied by using the resonant two-photon ionization (R2PI) technique. Recoil anisotropy parameters as well as average translational energy of the I atoms in the fine structure states P-2(1/2) and P-2(3/2) have been determined. The main contribution (99%) to the absorption at 266 nm was found to be caused by a parallel transition to the (3)Q(0) state which gives mainly excited-state atoms I(P-2(1/2)). The ground-state atoms I(P-2(3/2)) were found to appear mainly (88%) from the primarily excited (3)Q(0) state via curve-crossing (3)Q(0)-(1)Q(1) and to a lesser extent (12%) from direct absorption by a perpendicular transition to the (1)Q(1) and (3)Q(1) states. The fs pump-dump technique in combination with ns R2PI probing of the fragments I(P-2(1/2)) and I(P-2(3/2)) and time-of-flight mass spectrometry have been applied to probe the early stage dynamics of the C2F5I molecule on the excited state (3)Q(0) potential energy surface (PES). The evolution time of the excited molecule to the point where the energy gap between the excited state (3)Q(0) and the ground-state potential energy surfaces drops to a value of about 12 440 cm-1 was found to be 52 +/- 13 fs. This time corresponds to about 0.8 Angstrom extension of the C-I bond distance. The molecular dynamics simulation with DFT calculated ground-state PES and (3)Q(0) PES with the shape calculated for methyl iodide found in the literature gives reasonable agreement with the experimental result for the evolution time. (C) 2001 American Institute of Physics.
|Research areas and keywords||
Subject classification (UKÄ) – MANDATORY
|Journal||Journal of Chemical Physics|
|Publication status||Published - 2001|