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Excess Energy and Structural Dependence of the Rate of Energy Redistribution During the Photodissociation of Iodotoluenes.

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The ortho 2-, meta 3-1, and para 4- iodotolunes C7H7I photodissociated at 266 nm and 30.4 nm and studied with state-selective one- dimensional photo-fragment translational spectroscopy with state-selective velocity, and translational energy distributions are obtained for the ground I2P32 and spin-orbit excited state I2P12 iodine atoms produced photodissociation. As has been observed in iodobenzene, the ground state I channel observed in each isomer of iodotoluene exhibits both a prompt alkyl iodide-like dissociation channel following a parallel excitation to the alkyl iodide 30zeron, sigma repulsive state and curve crossing to the 1Q1n, sigma state, and a slower, indirect dissociation channel following a competitive excitation to aromatic charge transfer pi, pi predissociate excited states at both 266 nm and 304 nm. The I channel observed at both 266 nm and 304 nm for each isomer results from prompt dissociation resulting from parallel absorption to an alkyl iodide type 3Qzeron, sigma state. The rapid I and I dissociative channels observed for each isomer are found to exhibit strong dependence on the excess excitation. This is discussed in terms of the increase in the density of the vibrational states of the toluene ring. Dissociation times and rates of internal energy redistribution IER from the slow dissociative channel Beta are estimated for each isomer. For 2- iodotoluene, the rate of IER for the slow I channel increases from 20 kcalmol- ps at 304 nm to 30 kcalmol-ps at 266 nm, while the rates of IER for 3- and 4- iodotoluene 16 kcalmol-ps and 15 kcalmol-ps, respectively remain unchanged as the photon energy is increased

Subject Categories:

  • Inorganic Chemistry
  • Organic Chemistry
  • Radiation and Nuclear Chemistry
  • Atomic and Molecular Physics and Spectroscopy

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