Reactive Scattering of OxygenAtoms With Iodine Molecules

Abstract

Reactive scattering of O atoms with I2 molecules has been studied at an initial translational energy E~43 kJ mol−1 using cross-correlation time-of-flight analysis with resolution improved overprevious measurements. The broad centre-of-mass differential cross section favours the backward hemisphere with a product translational energy distribution lying above the distribution observed at lower initial translational energy but below the microcannonical RRHO distribution. However, a minor component with very low product translational energy favours the forward hemisphere. The observed scattering is attributed to a strongly bent OII triplet complex intermediate with a lifetime shorter than the period of overall rotation of the axis of the heavy II diatomic but long compared with the period of vibrational and rotational motion of the light O atom.

Reactive scattering of a supersonic fluorine atom beam: F + I2

“…The strong similarity in the form of the reactive scattering observed for the F + 12 reaction in the present study and that previously determined for the 0 + 12 reaction [19] in particular, suggests that migratory trajectories also contribute to the 0 + 12 reaction dynamics. In this case the triplet and singlet character of the 0 + 12 potential energy surface must vary along the migratory trajectory due to singlet-triplet mixing of the 012 electronic structure induced by increasing spin-orbit interaction as the 12 bond becomes extended [19]. For both reactions, therefore, the second well on the potential energy surface becomes accessible to migratory trajectories only as the I atoms begin to separate.…”

“…Scattering into the forward and backward hemispheres arises from the balance of migratory and nonmigratory trajectories and becomes increasingly differentiated with increasing initial translational energy. A similar situation also applies to the reactive scattering of 0(SP) atoms with Br/ [18] and I 2 [19] molecules where considerable similarity is also found with the predictions of a long-lived collision complex model [20]. Distinctions between the reactive scattering into the forward and backward hemispheres have also been Downloaded by [University of California Santa Barbara] at 11:07 16 June 2016 identified [18,19] for these reactions at higher initial translational energy.…”

“…A similar situation also applies to the reactive scattering of 0(SP) atoms with Br/ [18] and I 2 [19] molecules where considerable similarity is also found with the predictions of a long-lived collision complex model [20]. Distinctions between the reactive scattering into the forward and backward hemispheres have also been Downloaded by [University of California Santa Barbara] at 11:07 16 June 2016 identified [18,19] for these reactions at higher initial translational energy. It was proposed [18,19] that the reaction dynamics are long-lived with respect to motion of the light 0 atom but not with respect to rotation of the axis between the heavy halogen atoms.…”

“…Distinctions between the reactive scattering into the forward and backward hemispheres have also been Downloaded by [University of California Santa Barbara] at 11:07 16 June 2016 identified [18,19] for these reactions at higher initial translational energy. It was proposed [18,19] that the reaction dynamics are long-lived with respect to motion of the light 0 atom but not with respect to rotation of the axis between the heavy halogen atoms. However no firm conclusion could be drawn concerning the occurrence of migratory reaction dynamics.…”

“…A well may occur in the OXX (3A") configuration on the triplet potential energy surface of the reactants [24] and a second well in the bent XOX (1A1) configuration on an underlying singlet potential energy surface [25]. The strong similarity in the form of the reactive scattering observed for the F + 12 reaction in the present study and that previously determined for the 0 + 12 reaction [19] in particular, suggests that migratory trajectories also contribute to the 0 + 12 reaction dynamics. In this case the triplet and singlet character of the 0 + 12 potential energy surface must vary along the migratory trajectory due to singlet-triplet mixing of the 012 electronic structure induced by increasing spin-orbit interaction as the 12 bond becomes extended [19].…”