Gérard Parlant

Theoretical state-to-state cross sections for collisions of N2+ (X, υ) or N2+(A, υ) with Ar

Abstract State-to-state cross sections have been calculated for collisions of N + 2 (X, υ) or N + 2 (A, υ) with Ar at relative energies of 8 and 20 eV. The computations utilize potential energy surfaces computed recently by Archirel and Levy. In the calculations the translational motion is treated classically, and the time-dependent Schrodinger equation is solved exactly for the vibronic states of the system. In addition to the charge transfer and vibrational excitation and deexcitation processes, cross sections are also obtained for internal conversion between N + 2 (A) + Ar and N + 2 (X) + Ar. The results are in good agreement with the available experimental data at these energies.

Theoretical state‐to‐state charge transfer cross sections for collisions of Ar+ (2P3/2, 2P1/2) with N2

State‐to‐state cross sections have been calculated for collisions of Ar+(2P3/2, 2P1/2) with N2 over the relative collision energy range 1–4000 eV. The computations have been done by means of the vibronic semiclassical method recently used by Parlant and Gislason for N+2+Ar collisions. The translational motion is treated classically, and the time‐dependent Schrodinger equation is solved exactly for the vibronic states of the system. The potential energy surfaces utilized are those of Archirel and Levy. The results for the total charge transfer cross sections are in fairly good agreement with experimental data over the whole energy range. An unexpected participation of the A state of N+2 at low collision energy is observed. The charge transfer cross section ratio for the two spin–orbit states is discussed in a comparison with the available experimental data. In addition, the vibrational state distributions of N+2(X;v’) show good agreement with the recent measurements of Liao et al.

A new mechanism for providing stable molecular products in high energy reactions

Abstract A new mechanism for stabilizing product molecules in high-energy chemical reactions is described. It was discovered in quasi-classical trajectory studies of the reactions of Cl − +H 2 . It should apply to a wide range of reactions, and it may be the primary source of product molecules with internal energies well below the dissociation limit. It was quite different from the sequential impulse model, which can also give stable products.

A trajectory surface-hopping study of Cl− + H2 reactive collisions

Abstract A trajectory surface-hopping study has been carried out for collisions of Cl − + H 2 at a relative collision energy of 9.7 eV. Including the reactant channel, seven different product states were formed. A simple diatomics-in-molecules procedure has been used to construct the two lowest potential energy surfaces for the ClH − 2 system. In addition, a LEPS potential surface for neutral ClH 2 was used. It was assumed that the electron was immediately ejected whenever a trajectory on an ionic surface crossed the neutral surface. Total cross sections for the various product channels as well as differential cross sections, internal energy distributions, and doubly differential cross sections are presented. The results agree reasonably well with recent experimental studies of this system.

Theoretical state‐to‐state inelastic cross sections for collisions of Ar+(2P3/2, 2P1/2) with N2

State‐to‐state cross sections for fine‐structure transitions and vibrational excitation have been calculated for collisions of Ar+(2P3/2, 2P1/2) with N2 over the relative collision energy range 1–4000 eV. The computations were done by means of a vibronic semiclassical method, and the potential energy surfaces of Archirel and Levy were used. The cross sections are in good agreement with the limited amount of experimental data now available. The cross sections for fine‐structure transitions are surprisingly large at all energies.

Potential energy surfaces for the (ArCO)+ system

The five lowest doublet potential energy surfaces for the (ArCO)+ system have been determined using the procedure of Archirel and Levy. These states correlate at infinite separation, in order of increasing energy, to Ar+CO+(X 2Σ+), Ar+(2P3/2)+CO, Ar+(2P1/2)+CO, and Ar+CO+(A 2Π). The potential energy curves are shown at several values of the orientation angle. In addition, contour maps of the two lowest surfaces are presented. Both of these surfaces are quite anisotropic, and each has a deep potential well. Adiabatic vibronic potential energy surfaces have also been computed. These give insight into the charge transfer process at low collision energies. For the purpose of comparison the five lowest surfaces for the isoelectronic system (ArN2)+ are also shown.

Trajectory surface-hopping study of the K + O2 collision: Energy transfer in neutral and ionic products

Abstract The K + O2 collision has been studied at low energy by three-dimensional trajectory surface-hopping calculations. The diabatic potential energy surfaces used to describe the electronic states involved in the collision have been built using an analytical semi-empirical model and have not been fitted to experimental results. The double-peak structure experimentally observed in the energy-loss spectrum for K+ production is confirmed; but it appears that the high-energy-loss peak is due to efficient T-V energy transfer and not to electronic excitation of the O2− molecular ion. The energy transfer mechanism is explained by a comparison between the vibrational period of the target and the collision time which depends upon the collision energy.

Theoretical state‐to‐state cross sections for collisions of N+2(v)+Ar. II. Results at higher energies

State‐to‐state charge–transfer cross sections have been computed for N+2(X;v=0,1,2) +Ar at 12 collision energies between 1.2 and 320 eV. A classical path method is used, whereby the vibronic degrees of freedom are treated quantum mechanically as the system moves along a classical trajectory. The calculations use the potential energy surfaces computed by Archirel and Levy. Comparison is made with experimental results for this system, including the recent work from Ng’s laboratory. In most cases the agreement is quite good. There is, however, a significant difference in the charge–transfer branching ratios to produce Ar+(2P3/2) or Ar+(2P1/2) products. Possible explanations of the discrepancy are discussed. As expected, the cross sections obey the Franck–Condon principle at energies above 200 eV.

A trajectory surface-hopping study of Cl− + H2 reactive collisions. II. Results at high energy

Abstract A trajectory surface-hopping study has been carried out for collisions of Cl − + H 2 at relative collisions energies between 6 and 20 eV. In addition to total cross sections for producing the six product channels, we have computed a number of differential and doubly differential cross sections for the HCl products in reactive collisions at 20 eV. The results are compared with the predictions of a high-energy, sequential impulse model described in the companion paper.

Classical trajectory calculation for ion-pair formation in K+O2 collisions

Abstract Three-dimensional trajectory surface hopping calculations were performed on two diabatic energy surfaces. The covalent surface describes the K( 2 S) + O 2 ( 3 Σ − g ) state and the ionic surface K + ( 1 S) + O − 2 ( 2 Π g ). Transitions from one surface to another were computed through the Landau—Zener model. At small deflection angles, the energy loss distribution exhibits two peaks, as observed, due to O − 2 in its electronic ground state and to vibrationally excited O − 2 .