ABSOLUTE EMISSION CROSS-SECTIONS OF THE PASCHEN-ALPHA LINE AND PRODUCTION DYNAMICS OF THE 4F STATE OF THE EXCITED HYDROGEN-ATOM IN E-H-2 COLLISIONS

Absolute emission cross sections of the Paschen-alpha line from H (4S, 4P,4D,4F) produced in e-H-2 collisions have been determined to be 4.31 -10.1x10(-20) cm(2) at 20-100 eV by utilizing the Balmer-alpha emissio n cross sections as the standard; these values are about half those of the Balmer-beta emission. From these values, the formation cross sect ion of the 4F state has been first determined, together with the angul ar momentum distributions, which are the fraction of the formation cro ss sections of the 4S, 4P, 4D, and 4F state. The 4F state had apprecia ble cross sections at electron energies below 24 eV and was assigned t o be produced from the singly-excited states of H-2. In the doubly-exc ited state channel opening above 27-32 eV, the 4P and 4D states are pr eferentially produced, and the 4F state is suppressed. (C) 1997 Americ an Institute of Physics.