ANALYTIC CROSS SECTIONS FOR COLLISIONS OF H+, H2+, H3+, H, H2, AND H−WITH HYDROGEN MOLECULES

Analytic expressions fitted to cross section data on collisions of H+, H+2, H3+, H, H2, and H−with H2are given. The data used are those recommended by Phelps [J. Chem. Phys. Ref. Data 19, 653 (1990)] and additional experimental data, when available, up to a projectile energy of about 100 keV, including new kinds of reactions not treated by Phelps. The analytic expressions are of the semiempirical functional forms proposed by Green and McNeal [J. Geophys. Res. 76, 133 (1971)] and modifications of these, thus making it possible not only to interpolate but also to extrapolate the data to some extent.