An accurate total inelastic cross section for H2 + colliding with fast charged particles in the adiabatic approximation

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Abstract
A sum rule for the total inelastic cross section of H2 + colliding with fast charged particles is evaluated in the first Born approximation using the clamped nuclei [Born-Oppenheimer (B.O.)] wave function and the adiabatic wave function. The vibrational correction to this cross section is of almost the same magnitude for both wave functions, and its value is about 5 per cent of the total. The parameters for the sum rule which depend upon the internuclear distance R are evaluated from R=1·4 a 0 to R=2·6 a 0 for the B.O. wave function. These parameters are found to have better asymptotic behaviour for small R than for large R. The experimental values of the total cross sections of proton production processes measured by the swarm technique are twice as large as the theoretical ones. Calculations for various internuclear distances (i.e. for various excited vibrational states of the ground electronic state) are also compared with experiment. It is found that the proton production cross section mainly results from electron impact on H2 + molecules in the vibrationally excited electronic ground state. Assuming that v=2 is the most populous vibrational state, we find that the B.O. or adiabatic approximations to the wave function underestimate the experimental value of the cross section, which seems to indicate that rotational and vibrational excitation dissociation processes may make a significant contribution.