Experimental and theoretical studies of the gas-phase reactions of O(1D) with H2O and D2O at low temperature. Issue 45 (11th November 2021)

• Record Type: Journal Article
• Authors: Hickson, Kevin M.; Bhowmick, Somnath; Suleimanov, Yury V.; Brandão, João; Coelho, Daniela V.
• Is Part Of: Physical chemistry chemical physics. Volume 23:Issue 45(2021)
• Page Start: 25797
• Page End: 25806
• Publication Date: 2021-11-11
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d1cp04614d
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Measurements of the O( 1 D) + H2 O, D2 O reactions show that these processes become much more rapid below 100 K. Abstract : Here we report the results of an experimental and theoretical study of the gas-phase reactions between O( 1 D) and H2 O and O( 1 D) and D2 O at room temperature and below. On the experimental side, the kinetics of these reactions have been investigated over the 50–127 K range using a continuous flow Laval nozzle apparatus, coupled with pulsed laser photolysis and pulsed laser induced fluorescence for the production and detection of O( 1 D) atoms respectively. Experiments were also performed at 296 K in the absence of a Laval nozzle. On the theoretical side, the existing full-dimensional ground X 1 A potential energy surface for the H2 O2 system involved in this process has been reinvestigated and enhanced to provide a better description of the barrierless H-atom abstraction pathway. Based on this enhanced potential energy surface, quasiclassical trajectory calculations and ring polymer molecular dynamics simulations have been performed to obtain low temperature rate constants. The measured and calculated rate constants display similar behaviour above 100 K, showing little or no variation as a function of temperature. Below 100 K, the experimental rate constants increase dramatically, in contrast to the essentially temperature independent theoretical values. The possible origins of the divergence between experiment and theory at low temperatures are discussed.