The Bethe theory for dissociative excitations and ionisation of H2+(1sσg) by electron impact

Abstract

The revised Bethe theory due to Inokuti et al (1978) for the inelastic scattering of charged particles by atoms and molecules is applied to H2+ (1s sigma g). In the 'reflection' approximation, the cross sections for the sum of all the discrete excitations sigma ex, ionisation sigma i and total excitations sigma tot given in an asymptotic expression with the three constants (the so-called Born asymptote) instead of two constants (the so-called Bethe asymptote) are accurately calculated. The Bethe asymptotes are given for comparison with the less accurate ones reported by Peek (1974). It is shown that the ionisation cross sections given by the Born asymptote including the free-electron exchange correction are most compatible with the experimental data, but the ones given by the Bethe asymptote are only valid at high incident energies. The calculated sigma ex and sigma tot are also shown to be in excellent agreement with the experimental data at incident energies above 50 eV.