Wave packet and quasiclassical trajectory calculations for the N( 2 D)+H 2 reaction and its isotopic variants J.F. Castillo a , N. Bulut a,1 , L. Ban ˜ ares a, * , F. Gogtas b a Departamento de Quı ´mica Fı ´sica, Facultad de Quı ´mica, Universidad Complutense, 28040 Madrid, Spain b Firat University, Department of Physics, 23169 Elazi~ g, Turkey Received 25 September 2006; accepted 29 November 2006 Available online 3 December 2006 Abstract The N( 2 D)+H 2 (v = 0, j = 0) reaction and its HD and D 2 isotopic variants have been studied by means of quantum mechanical real wave packet and wave packet with split operator and quasiclassical trajectory methodologies on the potential energy surface of Ho et al. [J. Chem. Phys. 119 (2003) 6]. Total initial state-selected and final state-resolved reaction probabilities and product rotational distribu- tions have been calculated for total angular momentum J = 0 in a broad range of collision energies. The real wave packet results are in very good agreement with the corresponding split operator wave packet calculations. A reasonable overall good agreement has been found between the wave packet and quasiclassical trajectory results. Integral cross-sections and thermal rate constants have been calcu- lated from the wave packet reaction probabilities by means of standard J-shifting, refined J-shifting and uniform J-shifting methods in combination with the centrifugal sudden approximation for J > 0. Comparisons with available exact wave packet, quasiclassical trajec- tory and experimental results are made and discussed. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Reaction dynamics; Quasiclassical trajectory method; Wave packets; Insertion reactions 1. Introduction The N( 2 D)+H 2 elementary reaction is an important step in combustion processes and atmospheric chemistry. Several experimental and theoretical studies of the reaction have been carried out during the last 15 years. Unravelling the mechanism of the title reaction has been a process not exempt of controversy. In the early experimental work by Dodd et al. [1], the vibrational distribution of the nascent NH product was measured by time-resolved infrared emis- sion after a pulsed irradiation of an electron beam against a mixture of N 2 and H 2 . The ratio NH(v 0 = 1):NH(v 0 = 2): NH(v 0 = 3) was found to be 1.0:0.97:0.81 and also a NH(v 0 = 0):NH(v 0 = 1) ratio of 0.47 was indirectly derived. The measured inverted vibrational population was found to be indicative of a direct abstraction mechanism in a highly exothermic reaction. Kobayashi et al. [2] developed an ab initio potential energy surface (PES) for the ground state NH 2 system based on first order configuration inter- action (FOCI) calculations. The topology of this PES shows a barrier for the H–N–N linear configuration of 57 meV and a barrier for C 2v H–N–H configuration of 21.4 meV in the reactant valley. Subsequent quasiclassical trajectory (QCT) [2] and quantum mechanical (QM) [3] calculations on this PES predicted that the abstraction mechanism was dominant and inverted vibrational distri- butions of the products were obtained in agreement with experiment. However, the conclusions drawn from those experimen- tal and theoretical studies were contradicted by newer and more definitive sets of experiments and theoretical works that followed up. First, Umemoto et al. produced N( 2 D) atoms by photodissociation of NO and measured the 0301-0104/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.chemphys.2006.11.032 * Corresponding author. Tel.: +34 913944228. E-mail address: banares@quim.ucm.es (L. Ban ˜ ares). 1 On leave from: Firat University, Department of Physics, 23169 Elazi~ g, Turkey. www.elsevier.com/locate/chemphys Chemical Physics 332 (2007) 119–131