Experimental and theoretical kinetics for the H2O+ + H2/D2 → H3O+/H2DO+ + H/D reactions: observation of the rotational effect in the temperature dependence.
Thermal rate coefficients for the title reactions computed using a quasi-classical trajectory method on an accurate global potential energy surface fitted to ∼81,000 high-level ab initio points are compared with experimental values measured between 100 and 600 K using a variable temperature selected ion flow tube instrument. Excellent agreement is found across the entire temperature range, showing a subtle, but unusual temperature dependence of the rate coefficients. For both reactions the temperature dependence has a maximum around 350 K, which is a result of H2O(+) rotations increasing the reactivity, while kinetic energy is decreasing the reactivity. A strong isotope effect is found, although the calculations slightly overestimate the kinetic isotope effect. The good experiment-theory agreement not only validates the accuracy of the potential energy surface but also provides more accurate kinetic data over a large temperature range.
Space Vehicle Directorate, Air Force Research Laboratory, Kirtland AFB , Albuquerque, New Mexico 87117, United States.
Shaun G
SG
Ard
Anyang
A
Li
Oscar
O
Martinez
Nicholas S
NS
Shuman
Albert A
AA
Viggiano
Hua
H
Guo