Transition State Dynamics of O(3P) + OCS, CS2 Reactive Scattering at Initial Translational Energy E .apprx. 85 kJ mol-1

Abstract

Reactive scattering of ground state O(3P) atoms with OCS and CSz molecules has been studied at an initial translational energy E -85 kJ mol-' using a supersonic beam of 0 atoms seeded in He buffer gas generated from a high temperature radio frequency discharge source. The center-of-mass angular distribution of SO scattering for 0 + OCS is cone shaped peaking at a scattering angle 8 -70' with respect to the incident 0 atom direction, while that for 0 + CS2 peaks sharply in the forward direction 8 = 0". A similar fractionf' -0.3 of the total available energy is disposed into product translation for each reaction despite the substantial difference in exoergicities. The cone shaped scattering for 0 + OCS arises from direct dissociation of the early transition state which is formed by broadside approach of the 0 atom to the S atom of the OCS molecule. The sideways recoil of the SO product is carried into the forward hemisphere by the initial momentum of the 0 atom. The forward peaked scattering for 0 + CS2 arises from the precession of a weakly bound OSCS intermediate with a lifetime of one-third of a rotational period. In both cases reaction occurs over a 3A" potential energy surface involving planar bent cis or trans intermediates with bending mode excitation resulting in high product rotational excitation.

Dynamics of the Reaction O(3P) + H2S → OH + SH. 2. State-Resolved Differential Cross Sections and Angular Momentum Correlations

“…Sideways scattering in the direct O( 3 P) + OCS reaction has been attributed to side-on attack of the electrophilic O atom on the S followed by recoil along the breaking CS bond. 41 Such attack in the present system might be expected on the HOMO of the S atom, an out-of-plane p type orbital, but this would form a pyramidal transition state that is believed to lead to H + HSO products. 42 Furthermore, the present preference for one of the Λ doublets may indicate a plane of symmetry in the transition state.…”

Electron Irradiation of Carbon Disulfide-Oxygen Ices: Toward the Formation of Sulfur-Bearing Molecules in Interstellar Ices

“…Our kinetics scheme further proposes that the reaction of carbon disulfide (CS 2 ) with suprathermal atomic oxygen (O) can lead to the formation of carbon monosulfide (CS) and sulfur monoxide (SO), reaction (R4), via the "pickup" of a sulfur atom by the suprathermal oxygen atom. This mechanism was also identified as the major reaction pathway with fractions of up to 90% in the crossed molecular beam investigation of O( 3 P) with CS 2 (Rochford et al 1995), via the gas phase reaction of CS 2 and nascent oxygen (O) produced via the photolysis of nitrogen dioxide (NO 2 ) (Cheng et al 2001), and in the reaction between CS 2 and nascent oxygen (O) produced via the photolysis of ozone (O 3 ) in an argon matrix (Lo et al 2004):…”

“…The reaction of CS 2 with atomic oxygen (O) was also investigated in the gas phase. The crossed molecular beam reaction of CS 2 and atomic oxygen (O; 3 P) was studied via a single collision condition at a translational energy of 85 kJ mol −1 (Rochford et al 1995). The quadrupole mass spectroscopic detection revealed the formation of CS and SO as major reaction products under single collision conditions.…”

Reaction Dynamics of O(1D,3P) + OCS Studied with Time-Resolved Fourier Transform Infrared Spectroscopy and Quantum Chemical Calculations

“…Rochford et al performed crossed molecular beam experiments on O( 3 P) + OCS f SO + CO and found that the fraction of translational energy is ∼30% of the available energy. 7 They proposed that the cone-shaped scattering of SO arises from direct dissociation of an early transition state that is formed by a broadside approach of the O atom to the S atom of the OCS molecule; the reaction occurs over a triplet potential energy surface (PES) involving planar cis or trans bent intermediates; an extensive product rotational excitation is consequently expected. Shortridge and Lin employed resonance absorption with a CO laser to detect the vibrational population of CO product from mixtures of NO 2 /OCS/SF 6 upon UV (λ > 300 nm) photolysis and reported CO (V e 4) with a vibrational temperature of 9500 K, corresponding to 11% of the available energy.…”