DIFFERENTIAL CROSS-SECTIONS FOR THE ELECTRON-IMPACT EXCITATION OF N(3,1)S (N = 2, 3 AND 4) STATES OF HELIUM AT LOW ENERGIES

The 19-state and the 29-state R-matrix calculations are employed to ob tain the differential cross sections for the 1(1)S-n3,1S (n = 2, 3 and 4) excitation of helium at carefully chosen non-resonance energies ra nging from 22 to 29.6 eV. The scattering angle ranges from 0-degrees t o 180-degrees. The results of the calculation are compared with the la test experiments of Trajmar et al and Allan. Attempts are made to show that the angular distributions of scattered electrons of the same inc ident velocity that have excited the n3S(or n1S) levels of helium for n = 2, 3 and 4 are almost identical when fitted together at one angle.