Ab initio study of the lowest 3A′ and 3A″ potential energy surfaces involved in the O(3P) + CS(X1Σ+) → CO(X 1Σ+) + S (3P) reaction

Review of OCS gas-phase reactions in dark cloud chemical models

“…We find that the lowest energy singlet/triplet crossing point is for with a crossing point 30 kJ mol −1 above the triplet reactants S( 3 P) + CO. Table 2 reports the geometry and MRCI+Q energy of the lowest energy point of the singlet/triplet crossing seams between the 1 A′ PES and the 3 A′ or 3 A″ PES. Considering the high‐level method used for these theoretical calculations, the good agreement between the calculated and experimental OCS dissociation energies (Table 1) as well as the good agreement with previous calculations (Sayos et al 1990; Hijazo et al 1994; Gonzalez et al 1996; Adriaens et al 2010), our new ab initio calculations show that the and the reactions are in fact negligible at 10 K and cannot be a source of OCS in the ISM.…”

“…CASSCF calculations show that the interaction potential is less repulsive for non‐collinear approach for both PESs than for collinear approach. Potential wells have been found on these two PESs (Hijazo et al 1994; Gonzalez et al 1996) with the O–C–S angle (θ OCS ) close to 124°, but with energies of the equilibrium structures significantly higher than the S( 3 P) + CO dissociation limit.…”

“…There have been previous theoretical studies of this reaction. Some by the Sayos group at a moderate computational level MP2/6‐311(2d) (Hijazo, Gonzalez & Novoa 1994), MNDO/CI level (Sayos, Gonzalez & Aguilar 1990) and MP4 level (Gonzalez et al 1996)), and one more recently at a much higher level CCSD(T)/aug‐cc‐VQZ/CCSD(T)/aug‐cc‐VTZ (Adriaens et al 2010). These studies are in qualitatively good agreement even if there are some differences for the height of the activation barrier, between 6.7 and 18.7 kJ mol −1 , the latter value corresponding to the latest calculation at the highest level.…”

Dynamics of dissociative scattering: Hyperthermal energy collisions of state-selected OCS+ on Ag(111)

“…10. 34,35,50,51 If either of these electronic states are populated during neutralization, the triatom may impact the surface while the S and CO fragments are separating. Likewise, the 1 ⌸ level is unstable and dissociates into O and CS fragments.…”

“…In addition, the predissociative 3 A state can also be populated by resonant neutralization, but the 3 A electronic state exclusively yields S( 3 P) products. 51 To determine the dissociation mechanism and whether the S fragment intermediate is formed in a 1 D or 3 P state, we have scattered an atomic ion beam of state-selected S Ϫ ( 4 S) on Ag͑111͒ under the identical conditions as those used in the OCS ϩ (X 2 ⌸) study. As in many positive-ion scattering experiments on clean metal surfaces, we find neutralization to be efficient for the S ϩ ( 4 S) ion.…”