REACTION BETWEEN OH (OD) RADICALS AND CO AT TEMPERATURES DOWN TO 80-K- EXPERIMENT AND THEORY

Using the pulsed laser-photolysis (PLP) laser-induced fluorescence (LI F) method, rate constants have been measured at low total pressure for the reactions between OH and CO (297 greater-than-or-equal-to T/K gre ater-than-or-equal-to 80) and OD + CO (295 greater-than-or-equal-to T/ K greater-than-or-equal-to 178). Calculations have been carried out ba sed on transition-state and RRKM theories and allowing approximately f or quantum mechanical tunneling through the transition state (TS2) whi ch separates HOCO (DOCO) from H(D) + CO2. They indicate (a) that tunne ling is important in both these systems, (b) that the barrier at TS2 i s higher than previously thought and closer to the ab initio value, an d (c) that the observed kinetic isotope effect can be reproduced quite well. The possible role of hydrogen-bonded complexes in facilitating these reactions is discussed briefly.