Reactive scattering of a supersonic fluorine atom beam: F + C 3 H 5 I

Author: Harkin J.J.   Smith D.J.   Grice R.  

Publisher: Taylor & Francis Ltd

ISSN: 1362-3028

Source: Molecular Physics, Vol.72, Iss.4, 1991-03, pp. : 763-775

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Abstract

Reactive scattering of F atoms with C 3 H 5 I molecules has been studied at an initial translational energy E ∼ 38 kJ mol -1 using a supersonic beam of F atoms seeded in He buffer gas and at E ∼ 12 kJ mol -1 with Ne buffer gas. The centre-of-mass angular distribution of IF scattering at E ∼ 38 kJ mol -1 shows peaking in the forward and backward directions which is consistent with reaction via a short-lived F-I-C 3 H 5 complex with a lifetime less than one rotational period. The angular distribution at E ∼ 12 kJ mol -1 has a broad peak in the forward direction. The extended microcanonical theory shows that only a minor fraction of scattering at high initial translational energy may be identified with the precessional motion of the F-I-C 3 H 5 product transition state formed in large impact parameter collisions. However, a major fraction of scattering at E ∼ 38 kJ mol -1 and all the scattering at E ∼ 12 kJ mol -1 may be described by phase space theory. The product translational energy distributions indicate that energy is not randomized over internal modes of the intermediate complex in accord with previous laser-induced fluorescence measurements of the IF product vibrational state distribution. However, the overall distribution of internal energy which determines the product angular and translational energy distributions is compatible with the microcanonical distribution for an effective number of internal degrees of freedom.