2020-10-29T04:27:15Z
https://digital.csic.es/dspace-oai/request
oai:digital.csic.es:10261/65118
2019-09-11T10:32:20Z
com_10261_14181
com_10261_4
col_10261_14182
Dynamically biased statistical model for the ortho/para conversion in the H 2+H 3 + → H 3 + + H 2 reaction
Gómez Carrasco, Susana
González-Sánchez, Lola
Aguado, Alfredo
Sanz-Sanz, Cristina
Zanchet, Alexandre
Roncero, Octavio
In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H+ 5 complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasiclassical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H+ 5 complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice¿Ramsperger¿Kassel¿Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, ¿(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.
2013-01-25T11:53:06Z
2013-01-25T11:53:06Z
2012
2013-01-25T11:53:06Z
artículo
Journal of Chemical Physics 137: 094303 (2012)
http://hdl.handle.net/10261/65118
dx.doi.org/10.1063/1.4747548
eng
openAccess
American Institute of Physics