New ab initio potential energy surface and quantum dynamics of the reaction H(2S) + NH(X3Σ) → N(4S) + H2.
ABSTRACT A new global potential energy surface is reported for the ground state ((4)A(")) of the reaction H((2)S) + NH(X(3)Σ()) → N((4)S) + H(2) from a set of accurate ab initio data, which were computed using the multireference configuration interaction with a basis set of augccpV5Z. The manybody expansion and neural network methods have been used to construct the new potential energy surface. The topographical features of the new global potential energy surface are presented. The predicted barrier height is lower than previous theoretical estimates and the heat of reaction with zeropoint energy is closer to experimental results. The quantum reactive scattering dynamics calculation was carried out over a range of collision energies (01.0 eV) on the new potential energy surface. The reaction probabilities, integral crosssection, and rate constants for the title reaction were calculated. The calculated rate constants are in excellent agreement with the available experimental results.

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ABSTRACT: In this work, quasiclassical trajectory (QCT) calculations have been first carried out for the title reaction on a new global potential energy surface for the lowest quartet electronic state, 4A″. The average rotational alignment factor [P 2( j' · k )] as a function of collision energy and the two commonly used polarization dependent generalized differential cross sections PDDCS00, PDDCS20, have been calculated in the centerofmass (CM) frame, separately. Three angular distributions, P( r), P(φ r), and P( r, φ r) are also calculated to gain insight into the alignment and the orientation of the product molecules. Calculations show that the average rotational alignment factor on the ZH PES is almost invariant with collision energies. The distributions of P( r) and P(φ r) derived from the title reaction indicate that the product polarization is strong. Validity of the QCT calculation has been examined and proven in the comparison with the quantumwavepacket calculation results. Comparisons with available quasiclassical trajectory results are made and discussed.Canadian Journal of Chemistry 01/2013; 91(6). DOI:10.1139/cjc20120404 · 1.01 Impact Factor 
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ABSTRACT: We show theoretically that ultracold hydrogen atoms have very favorable properties for sympathetic cooling of molecules to microkelvin temperatures. We calculate the potential energy surfaces for spinpolarized interactions of H atoms with the prototype molecules NH(^{3}Σ^{}) and OH(^{2}Π) and show that they are shallow (50 to 80 cm^{1}) and only weakly anisotropic. We carry out quantum collision calculations on H+NH and H+OH and show that the ratio of elastic to inelastic cross sections is high enough to allow sympathetic cooling from temperatures well over 1 K for NH and around 250 mK for OH.Physical Review Letters 11/2013; 111(20):203004. DOI:10.1103/PhysRevLett.111.203004 · 7.73 Impact Factor 
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ABSTRACT: The stereodynamics and reaction mechanism of the H'(2S) + NH (X3Σ) → N(4S) + H2 reaction are thoroughly studied at collision energies in the 0.1 eV1.0 eV range using the quasiclassical trajectory (QCT) on the ground 4A″ potential energy surface (PES). The distributions of vector correlations between products and reagents P(θr), P(φr) and P(θr, φr) are presented and discussed. The results indicate that product rotational angular momentum j' is not only aligned, but also oriented along the direction perpendicular to the scattering plane; further, the product H2 presents different rotational polarization behaviors for different collision energies. Furthermore, four polarizationdependent differential cross sections (PDDCSs) of the product H2 are also calculated at different collision energies. The reaction mechanism is analyzed based on the stereodynamics properties. It is found that the abstraction mechanism is appropriate for the title reaction.