Collisions of excited Na atoms with H2 molecules. I. A b i n i t i o potential energy surfaces and qualitative discussion of the quenching process

Abstract

Articles you may be interested inA potential energy surface for the process H2+H2O→H+H+H2O : A b i n i t i o calculations and analytical representation J. Chem. Phys. 94, 2986 (1991); 10.1063/1.459822 Inelastic scattering calculations in polyatomic systems using an a b i n i t i o intermolecular potential energy surface. II. Rotational energy transfer in CO2-H2 collisions Crossed beam studies of the dynamics of electronic energy transfer: Quenching of Na(3p 2 P 3/2) atoms by N2, O2, CO, and NO molecules Potential energy surfaces have been calculated for the four lowest electronic states of Na (3 's, 3 'P) + H,('I/) by means of the RHF-SCF and PNO-CEPA methods. For the so-called quenching process ofNa (3 'P) by H, at low initial translational energies (E-VRTenergy transfer) the energetically most favorable path occurs in C" symmetry, since-at intermediate Na-H, separation-the X, B, potential energy surface is attractive. From the CEP A calculations, the crossing point of minimal energy between the X' A ,andX'B, surfaces is obtained at R, == 3.57 a.u. and r, == 2.17 a.u. with an energy difference to the asymptotic limit (R == 00, r == re) of -0.06 eV. It is thus classically accessible without any initial translational energy, but at low initial translational energies (~O.l e V) quenching will be efficient only for arrangements of collision partners close to C" symmetry. There is little indication of an avoiding crossing with an ionic intermediate correlating asymptotically with Na+ and H, as was assumed in previous discussions of the quenching process. The dependence of the total quenching cross sections on the initial translational energy is discussed by means of the "absorbing sphere" model, taking the initial zero-point vibrational energy of the hydrogen molecule into account. New experimental data of the product channel distribution in H, for centerof-mass forward scattering are presented. The final vibrational states v' == 3, 2, I, and 0 of H, are populated to about 26%,61%,13%, and 0%, respectively. The observed distributions in H, (and D,) may be rationalized by simple dynamic considerations on the basis of the calculated surfaces.5438

Interfacing Electronic Structure Theory with Dynamics

“…There has been considerable recent interest in the possible existence of weakly interacting complexes between the lighter metals M in the second and third periods and clusters of molecular hydrogen. [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] Here, we focus on M ) Al.…”

Structure and Stability of M−H2 Complexes

“…[6][7] A minimum with D e about 10 kcal/mol was found on the 2 B 2 surface, and the transition from 2 B 2 to 2 A 1 was predicted to occur with high probability. Potential energy surfaces have also been studied for Na-H 2 , [8][9][10] Be-H 2 , 11-13 and Mg-H 2 13-15 excited states. Augspurger and Dykstra found van der Waals complexes for Mg-H 2 and Mg-HF ground states using the coupled cluster method and triple-zeta quality basis sets.…”

Evolutionary algorithms and their application to optimal control studies

“…Figure 8.1 shows a cut through the ground (X 2 A 1 ) and first electronically excited (A 2 B 2 ) PES of the NaH 2 collision system in C 2v symmetry. This symmetry gives the largest contribution for the quenching process as has been shown by Botschwina [168] and de Vivie-Riedle et al [169]. A qualitative description based upon ab-initio calculations has been given by Botschwina [168] in the context of the "bond-stretch-attraction" model.…”

“…This symmetry gives the largest contribution for the quenching process as has been shown by Botschwina [168] and de Vivie-Riedle et al [169]. A qualitative description based upon ab-initio calculations has been given by Botschwina [168] in the context of the "bond-stretch-attraction" model. To achieve a bound PES via the wave function overlap between the Na(3p) lobes and the H 2 orbitals, the p-orbital must be aligned parallel to the H 2 axis, whereas the remaining two p-orientations lead to repulsive PES.…”

“…The non-adiabatic crossing takes place via a conical intersection, vide infra. (c) Since only three atoms are involved in this reaction, with H 2 being the simplest conceivable molecule and sodium a hydrogen-like atom with only one outer shell electron, a theoretical simulation of the atom-molecule system with only three internal degrees of freedom is feasible [160,[163][164][165][166][167][168][169]. After excitation of the unbound (Na(3s)+H 2 ) system with a red-detuned laser pulse, a bound collision complex (Na(3p)+H 2 ) is formed (exciplex) with a well depth of 0.4 eV [159], due to the wave function overlap of the orbital of the H 2 molecule and the lobes of the valence electron of the Na(3p) atom [168].…”