Orientation dependence of the F + H2 and H + F2 reactions using the line-of-centres model with angle-dependent collision diameters and barrier heights

Abstract

We have extended our earlier work on the validity of the angle-dependent line-of-centres (ADLOC) model in two ways. First, we have obtained a new effective ϕ-dependent barrier height, by inverting quasiclassical trajectory (QCT) data calculated for a fixed angle of attack, ϕ. Secondly, we have allowed the collision diameter, D, to depend on ϕ, by assuming that D(ϕ) is an ellipse. The two parameters A and B of the ellipse are used to least-squares fit the ADLOC cross-sections to QCT excitation functions for the F + H₂(v= 0, j= 0) and H + F₂(v= 0, j= 0) reactions. Two additional angle-dependent barrier heights have also been employed in these calculations. For both reactions, excellent fits of the ADLOC model to the QCT cross-sections are obtained at all energies. However, the values of A and B can differ significantly, depending on the angle-dependent barrier height that is used.