Average H–H2 Repulsive Potential from Collision Cross Section Measurements

The average repulsive potential between a hydrogen atom and a hydrogen molecule has been computed from experimental values of elastic collision cross sections for fast hydrogen atoms (with energies of 200 to 800 electron volts) scattered in room temperature molecular hydrogen. It was possible to solve the classical theory scattering equations explicitly for the repulsive potential by proper analytical representation of the experimental cross section values as a function of the relative kinetic energy of the scattering system. The potential function so obtained predicts total collision cross sections within the experimental error and has the form V(r)=A exp (−ar2)+B exp (−br2) where r, the distance between the mass points representing the hydrogen atom and the hydrogen molecule, extends, in the present case, from 0.28 to 0.70A. For r in A units, A = 0.846×10−10 erg, a = 24.9A−2, B = 0.211×10−10 erg and b = 2.40A−2.