Role of Renner Teller and Spin−Orbit Interaction in the Reactive Scattering of O(³P) Atoms with CF₃I Molecules

Abstract

Reactive scattering of O( 3 P) atoms with CF 3 I molecules has been studied at initial translational energies E ∼ 108 and 42 kJ mol -1 using supersonic beams of O atoms seeded in He buffer gas generated from rf and microwave discharge sources. At the higher initial translational energy, the IO scattering shows a broad peak in the forward hemisphere with respect to the initial O atom direction with a product translational energy distribution shifted to higher energy than the prediction of phase space theory. At the lower initial translational energy, the IO scattering shows a sideways peaked component with a fraction f ′ ∼ 0.4 of the total available energy being disposed into translation and a forward and backward peaked component with a product translational energy distribution in accord with the predictions of phase space theory. The sideways scattering is attributed to direct reaction over the triplet 3 A′′ potential energy surface, while the forward and backward peaked scattering is attributed to dissociation of a persistent singlet OICF 3 complex formed by intersystem crossing to the underlying 1 A′ potential energy surface. The direct scattering over the triplet 3 A′′ potential energy surface contributes a fraction, ∼0.5, to the total reaction cross section at the lower initial translational energy, while the forward scattering at the higher initial translational energy is dominated by direct reaction over the triplet 3 A′′ potential energy surface. This dynamical behavior is correlated with the effect of charge transfer interaction of the form OI + Ron Renner Teller splitting of the triplet potential energy surface.

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(3P) + CH2ICl Reaction

“…The IO product scattering from the O + CF 3 I reaction has also been resolved into two components recently 4 Figure 8 illustrates the Renner Teller splitting 20 of the triplet 3 Π potential energy surface as a function of the OIC interbond angle β where β ) 180°denotes the collinear configuration. In…”

“…Recent crossed molecular beam studies − of the reactive scattering of ground-state O( 3 P) atoms with alkyl and allyl iodide molecules have shown the importance of intersystem crossing from the initial triplet potential energy surfaces to the underlying singlet potential energy surface. Direct dynamics over the triplet potential energy surface result in IO product formed with high translational energy, whereas the singlet potential energy surface supports a long-lived OIR intermediate complex that yields IO product with low translational energy and in some cases ,,, HOI product formed via a five-membered ring transition state.…”

“…Direct dynamics over the triplet potential energy surface result in IO product formed with high translational energy, whereas the singlet potential energy surface supports a long-lived OIR intermediate complex that yields IO product with low translational energy and in some cases 1,2,6,7 HOI product formed via a five-membered ring transition state. In the case of alkyl and allyl iodides, [1][2][3] the direct scattering appears as enhanced backward scattering of IO product, whereas enhanced sideways scattering is observed 4 for CF 3 I and little 5 direct scattering is observed for CF 3 CH 2 I. This variation in the direction and extent of direct IO scattering has been related 4 to the effect of charge transfer interaction of the form OI + Ron the Renner Teller splitting of the triplet potential energy surface in strongly bent configurations.…”

“…In the case of alkyl and allyl iodides, [1][2][3] the direct scattering appears as enhanced backward scattering of IO product, whereas enhanced sideways scattering is observed 4 for CF 3 I and little 5 direct scattering is observed for CF 3 CH 2 I. This variation in the direction and extent of direct IO scattering has been related 4 to the effect of charge transfer interaction of the form OI + Ron the Renner Teller splitting of the triplet potential energy surface in strongly bent configurations. To test the validity of this hypothesis, studies have been undertaken on further substituted iodomethane molecules varying the electron affinity of the departing radical R. Results are reported here on the reaction of chloroiodomethane molecules that may also be of some significance in the iodine chemistry of the upper atmosphere 8 :…”

Role of intersystem crossing in the reactive scattering of O( 3P) atoms with CH 2I 2 molecules

“…Dissociation of the long-lived singlet OIR complex forms IO product with low product translational energy or, in some cases, HOI product via a Ðve-membered-ring transition state.1,2,6,7 However, IO product may also be formed with high product translational energy by direct reaction dynamics over the triplet potential-energy surface, yielding backward peaked scattering from nearly collinear OIR conÐgurations8 and sideways scattering from strongly bent OIR conÐgurations. 4 The balance of these contributing pathways depends on the substituted methyl radical, R, and the way that this inÑuences the form of the reaction potential-energy surfaces involved. Thus, the formation of HOI product depends1,2,6,7 upon the presence of a hydrocarbon chain with b hydrogen atoms, which can be abstracted by the pendant O atom of the singlet OIR intermediate.…”