Cross sections for excitation of the b3Σ+u, a 3Σ+g, and c3Πu states of H2 by low-energy electrons

We used a multichannel extension of the Schwinger variational principle [K. Takatsuka and V. McKoy, Phys. Rev. A 24, 2473 (1981)] to study the cross sections for excitation of the X ¹ Σ⁺_g-->b ³Σ⁺_u, a ³Σ⁺_g, and c³Π_u transitions in H₂ by low-energy electrons. These cross sections were obtained with two open channels for each transition and for energies near threshold to 30 eV. The results for the b³Σ⁺_u and a ³Σ⁺_g states agree quite well with available experimental data. However, the cross sections for excitation of the c ³Π_u state differ significantly from the measured values at the two energies, 20 and 30 eV, where data are available.