Potential energy surfaces related to the ion-molecule reaction C+ + H2

Abstract

+ .The C + H2 10n-molecule reaction has been studied by several experimental groups and appears destined to become the focal point of much experimental and theoretical activity. Ab initio self-consistent-field and configuration interaction calculations have accordingly been carried out for this system. A double zeta basis set of contracted gaussian functions was employed and as many as 570 confiqurations included. For isosceles triangle configurations (C 2V point group) 2 2 2 the AI' B l , and B2 potential surfaces were considered, while for linear geometries (C wv ) the 2E+ and 2rr surfaces were studied. Properties reported include minimum energy paths and energy profiles for the various processes considered. The intuitive correlation diagram of Mahan and Sloane is made semiquantitative in reliability.

Rate coefficients for the endothermic reactions C+(2P)+H2(D2)→CH+(CD+)+H(D) as functions of temperature from 400–1300 K

“…50 This result is consistent with ab initio calculations, [9][10][11][12] which show that only two of the six nearly degenerate electronic states available to the reactants can lead to reaction under thermal conditions because of high energy barriers on the other four adiabatic potential surfaces. This would lead to an electronic degeneracy factor of 2/6 if one ignores the spinorbit splitting and assumes that all six states are equally populated in the entrance channel, although somewhat higher factors are possible under other scenarios.…”

“…Fourth, the reaction is of astrophysical significance as a possible source of the CH ϩ ions observed in interstellar clouds. [1][2][3][4][5][6][7][8] Consequently, this system has been the subject of numerous theoretical studies, including ab initio potential energy surface computations, [9][10][11][12][13][14] classical trajectory studies, 15,16 and phase space [17][18][19][20][21] and transition state 22 theory calculations.…”

H2(v= 0,1) + C+(2P) → H+CH+STATE-TO-STATE RATE CONSTANTS FOR CHEMICAL PUMPING MODELS IN ASTROPHYSICAL MEDIA

“…Up to now, the experimental studies of this reaction (Gerlich et al 1987;Hierl et al 1997;Maier 1967;Frees et al 1979;Mahan & Sloane 1973;Herbst et al 1975;Harris et al 1975;Jones et al 1977;Zamir et al 1981;Ervin & Armentrout 1986;Glenewinkel-Meyer et al 1995) have provided information on the integral cross sections and the thermal rate constants and they have been successful in separating the contributions of vibrationally excited H 2 in the levels v = 0 and v = 1. From the theoretical point of view, several ab initio potential energy surfaces (PESs) have been computed (Liskow et al 1974;Sakai et al 1981;Saxon & Liu 1983;Stoecklin & Halvick 2005;Warmbier & Schneider 2011) and many dynamical studies have been performed using quasi-classical trajectories (QCT; Sullivan & Herbst 1978;González et al 1985) as well as phase space and transition state theory (Truhlar 1969;Chesnavich et al 1984;Ervin & Armentrout 1986;Gerlich et al 1987). In addition, the reverse reaction has also been analyzed using QCT (Halvick et al 2007;Warmbier & Schneider 2011) and a time-independent negative imaginary potential method (Stoecklin & Halvick 2005).…”

Spin-orbit quenching of the C+(2P) ion by collisions with para- and ortho-H2

“…7,8 They performed calculations of the spin orbit excitation cross sections of C + in collisions with both paraand ortho-H 2 . They obtained the angular dependence of the long-range potential expansion from the standard perturbation theory and derived the same expansion at short range, from available potential energy curves (PECs) 9 in linear and perpendicular approaches. This elegant approach was used later on for studying similar cationic systems, for example, Ne + ( 2 P) + H 2 .…”