A 19-STATE R-MATRIX INVESTIGATION OF RESONANCES IN E--HE SCATTERING AT LOW ENERGIES .4. 1(1)S-2(1)P DIFFERENTIAL CROSS-SECTIONS AND THE ELECTRON-PHOTON COINCIDENCE PARAMETERS LAMBDA AND VERTICAL-BAR-CHI-VERTICAL-BAR

Fon and Lim have reported the 11-state and 19-state R-matrix calculati ons of 1(1)S-2(3,1)S and 1(1)S-2(3)P differential cross sections at lo w energies. In this paper, the same R-matrix calculations are extended to obtain the differential cross sections and the electron-photon coi ncidence parameters lambda and \chi\ for the excitation of the ground state helium to the 2(1)P state. Convergence studies are carried out b etween the 11-state and 19-state R-matrix calculations. Only the 19-st ate R-matrix results are presented in full at scattering angles of 20- degrees, 30-degrees, 60-degrees, 90-degrees, 120-degrees and 140-degre es from the excitation threshold up to 23.8 eV. The calculations are p erformed at more than seven hundred energy points to reproduce previou sly observed resonant profiles.