ACCURATE FIRST BORN APPROXIMATION CROSS SECTIONS FOR EXCITATION OF HELIUM BY FAST ELECTRONS

Accurate first Born approximation cross sections are given for the electron impact excitation of the ground state of helium to the n 1S (n = 2 to 7), n 1P (n = 2 to 6) and n 1D (n = 3 to 6) excited states. Many-parameter correlated wave functions for both the initial and final states have been employed in the length formulation of the Born approximation integrals to obtain cross sections for excitation to the n 1S (n = 2 to 7), n 1P (n = 2, 3, 4) and 3 1D states. Calculations have also been performed in both length and velocity formulations using a six-parameter ground-state wave function and unrestricted Hartree-Fock excited-state wave functions. The results are compared with other calculations and with experiment.