PRODUCT BRANCHING RATIOS OF THE REACTION OF CO WITH H3+ AND H2D+

The reaction of CO with H-3(+) and H2D+ has been studied to investigate thermal rate coefficients and product branching ratios in the temperature range [20, 350] K, by using a direct ab initio molecular dynamics method. In trajectory simulations, the energies and forces are calculated using a scaling all correlation second-order M phi ller-Plesset perturbation theory (SAC-MP2) method with the correlation consistent polarized valence triplet-zeta basis (cc-pVTZ). Results show that total thermal rate coefficients for both the CO + H-3(+) and the CO + H2D+ reactions have a weakly positive temperature dependence. At room temperature, the rate coefficients are predicted to be (1.42 +/- 0.03) x10(-9) cm(3) molecule(-1) s(-1) with a product branching ratio of [HOC+]/[HCO+] = 0.36 +/- 0.01 for the CO + H-3(+) reaction, and (1.26 +/- 0.03) x 10(-9) cm(3) molecule(-1) s(-1) with the product branching ratios: 0.37 +/- 0.01 (([HOC+] + [DOC+])/([HCO+] + [DOC+])), 0.54 +/- 0.02 ([DCO+]/[HCO+]), and 0.49 +/- 0.02 ([DOC+]/[HOC+]) for CO + H2D+. The product branching ratios have a noticeable temperature dependence as well as a pronounced isotopic effect for the H/DOC+ product channel.