Electron excitation cross sections for multiply charged ions. Progress report, March 1, 1976--February 28, 1977

Collision strengths for electron impact excitation of lithium-like carbon and argon are calculated for energies up to three times threshold energies for transitions 2s-2p, 2l-3l, where l equals 0, 1 and l' equals 0,1 and 2. A partial wave expansion for the incident electron wave function is made. For an electron with low orbital angular momentum, a closely-coupled expansion method over the 2s, 2p, 3s, 3p, and 3d states of the ion is necessary in order to obtain an accuracy of 10 percent. Resonance structure in the collision strength below the n equals 3 threshold is being investigated by direct calculation and by extrapolation from above the n equals 3 threshold. A pseudostate calculation for He+, in which 1s, 2s, 2p, anti 3s and anti 3p functions are included in a close-coupling approximation, gives results for 1s yields 2s excitation which agree with experiment above 70 eV. The pseudostates are chosen to maximize their overlap with bound states and low-lying continuum states of the same symmetry. The algebraic variational method, which permits the inclusion of a large number of pseudostates where required, is being extended to ionic systems