Cross sections for electron impact excitation of the b ³σ _u⁺ state of H₂: An application of the Schwinger multichannel variational method

In this and two accompanying letters, the results of calculations of the cross sections for electron impact excitation of the b ³ Sigma _u⁺ state of H₂, for collision energies from near threshold to 30 eV, are presented. The results are obtained using a multichannel extension of the Schwinger variational principle at the two-state level. The quantitative agreement between the integral cross sections of these three studies is very good. Inclusion of correlation terms in the scattering wavefunctions, which relax the orthogonality between bound and continuum orbitals is seen to affect the cross sections substantially. Although a comparison of these calculated cross sections with available experimental data is encouraging, some serious discrepancies exist.