The use of second-order potentials in the theory of scattering of charged particles by atoms. VIII. The excitation of the n=3 levels of helium by electron and proton impact

For pt.VII see abstr. A47875 of 1974. Cross sections for the excitation of helium from the ground state to the 3 1 S, 3 1 P and 3 1 D levels, by electrons with energies in the range 100 to 1000 eV and by protons with energies in the range 50 to 1000 keV, have been calculated in a distorted wave approximation. The wavefunction in the incident channel was taken from a previous calculation employing a second-order effective potential and in the final state the effect of coupling between the n=3 levels was included. In the case of excitation of the 3 1 D level, it is shown that transitions via the 2 1 P intermediate state are important over the whole range. The calculated values are compared with those obtained from experiment and generally satisfactory agreement was found.