Absolute emission cross sections of the Paschen-α line and production dynamics of the 4F state of the excited hydrogen atom in e-H₂ collisions

Absolute emission cross sections of the Paschen-α line from H (4S,4P,4D,4F) produced in e-H₂ collisions have been determined to be 4.31-10.1 × 10^-20 cm² at 20-100 eV by utilizing the Balmer-α emission cross sections as the standard; these values are about half those of the Balmer-β emission. From these values, the formation cross section of the 4F state has been first determined, together with the angular momentum distributions, which are the fraction of the formation cross sections of the 4S, 4P, 4D, and 4F state. The 4F state had appreciable cross sections at electron energies below 24 eV and was assigned to be produced from the singly-excited states of H₂ . In the doubly-excited state channel opening above 27-32 eV, the 4P and 4D states are preferentially produced, and the 4F state is suppressed.