Issue 4, 2000

Dynamics of ionization processes of the ethylene–HF complex: a direct ab-initio dynamics study

Abstract

Ionization processes of the ethylene–HF (C2H4–HF) complex have been studied by means of both ab-initio molecular orbital and direct ab-initio dynamics methods. The ab-initio calculations of C2H4–HF show that the H-end of HF orients toward the center-of-mass of C2H4 by the dipole interaction (i.e. the H-orientation form). For the ionized state of C2H4–HF, it was found that the cation complex [C2H4–FH]+ with a planer structure is formed as the most stable form. The potential energy curve (PEC) calculated as a function of C2H4–HF center-of-mass distance (Rcm) indicates that the HF molecule is weakly bound on C2H4 at the neutral state, whereas the PEC for the cation system constrained to the H-orientation form is entirely repulsive. On the other hand, the PEC constrained to the F-orientation form is strongly bound. Also, it was found that the complex on PES at the ground state has a wide Franck–Condon region for the ionization. The direct ab-initio dynamics calculations (HF/6-311G(d,p) level) have been carried out for the ionization dynamics of C2H4–HF. The calculations showed that two reaction channels were obtained as products: one is a complex formation channel in which the complex composed of C2H4+–FH was formed, and the other one is a dissociation channel in which the trajectory leads to directly the dissociation product C2H4++HF without complex formation. The mechanism, in particular the preference for the reaction channels, is discussed on the basis of the theoretical results.

Article information

Article type
Paper
Submitted
13 Sep 1999
Accepted
19 Nov 1999
First published
03 Feb 2000

Phys. Chem. Chem. Phys., 2000,2, 839-845

Dynamics of ionization processes of the ethylene–HF complex: a direct ab-initio dynamics study

H. Tachikawa, Phys. Chem. Chem. Phys., 2000, 2, 839 DOI: 10.1039/A907395G

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