Global 1 ¹A″ potential energy surface of CH₂and quantum dynamics of a sideways insertion mechanism for the C(¹D) + H₂→ CH(²Π) + H reaction

Abstract

A global adiabatic potential energy surface (PES) corresponding to the second singlet state 1 1A" (1 1B1) of CH2 has been computed in a similar way as the first singlet state 1 1A' in our previous work [B. Bussery-Honvault et al., J. Chem. Phys., 2001, 115, 10 701]. This PES has a calculated well depth of 79.9 kcal mol(-1) relative to the C(1D) + H2 asymptote and correlates to CH(2pi) + H. It presents large barriers in the C(1D) + H2 arrangement for both collinear and perpendicular geometries but no barrier for geometries about 60 degrees and leads to a sideways insertion mechanism for the reaction C(1D) + H2 --> CH(2pi) + H. The ab initio calculations were carried out for 4644 geometries and the resulting energies were fitted to a many-body expansion. Accurate three-dimensional quantum mechanical scattering calculations have been performed for the C(1D) + H2(v = 0, j = 0) reaction on this ab initio 1 1A" PES in the collision energy range [0-11.5 kcal mol(-1)]. The J = 0 reaction probabilities show dense resonance structures as those obtained with the 1 1A' PES. However some different dynamical features have been found.

Dynamics of the C(1D)+H2reaction: A comparison of crossed molecular beam experiments with quantum mechanical and quasiclassical trajectory calculations on the first two singlet (11A′ and 11A″) potential energy surfaces

“…For this system, in fact, the interaction of the fivefold degenerate C( 1 D) atom with H 2 generates five singlet PESs, three of which (1 1 A 0 , 2 1 A 0 and 1 1 A 00 , corresponding to 1 1 A 1 , 2 1 A 1 and 1 1 B 1 , respectively, in the C 2v point symmetry group) are bound with respect to the reagent asymptote [14,17]. Amongst them, only the adiabats 1 1 A 0 and 1 1 A 00 PESs correlate with the ground-state CH(X 2 Å) product, while the 2 1 A 0 PES correlates with the highly excited A 2 D state of CH [14,17]. A fully ab initio 1 1 A 0 CH 2 PES has recently been derived by Bussery-Honvault, Honvault and Launay (BHL) [17] and widely employed in different types of scattering calculations [9,[18][19][20][21][22][23][24][25].…”

“…may also be affected by a reactive contribution originating from the first excited singlet CH 2 PES [14][15][16]. For this system, in fact, the interaction of the fivefold degenerate C( 1 D) atom with H 2 generates five singlet PESs, three of which (1 1 A 0 , 2 1 A 0 and 1 1 A 00 , corresponding to 1 1 A 1 , 2 1 A 1 and 1 1 B 1 , respectively, in the C 2v point symmetry group) are bound with respect to the reagent asymptote [14,17].…”

Ultra-Low-Temperature Reactions of Carbon Atoms With Hydrogen Molecules

“…However, the prediction of the reaction rates at low temperatures, based on the high temperature results, is often an origin of large errors. At the moment, there are no experimental studies of these reactions at low temperatures, while all quantum chemical computations performed do not find any notable energy barrier in the reaction pathways (Bussery-Honvault et al 2005, Harding et al 1993, Lin & Guo 2004. Additionally, there is a lack of data for the reaction of HCH molecules with dihydrogen (Ge et al 2010).…”

Ring-Polymer Molecular Dynamics for the Prediction of Low-Temperature Rates: An Investigation of the C(1D) + H2 Reaction

“…Honvault et al49 for the first excited state ( 1 A ′′ ) which were obtained from ab initio data using similar fitting methodologies. Both PESs exhibit barrierless minimum energy paths in the entrance channel (perpendicularly constrained approach and bent approach of C towards H 2 around 60 • for 1 A ′ and 1 A ′′ , respectively) and both are of insertion type with deep wells (4.32 and 3.46 eV relative to the reactants for 1 A ′ and 1 A ′′ , respectively).…”