DIFFERENTIAL CROSS-SECTIONS FOR THE ELECTRON-IMPACT EXCITATION OF HYDROGENLIKE CARBON

We report on a study of total and differential excitation cross sectio ns for the electron-impact excitation of hydrogenlike carbon for the t ransitions 1s(2)S --> 2s(2)S and 2p(2)P. These calculations have been performed for electron-impact energies ranging from 28.2 to 29.5 Ry us ing the close-coupling R-matrix method. This energy region has been ch osen because in addition to the direct excitation of 2s and 2p, there is a sizable contribution to the excitation cross section from the dou bly excited two-electron states (3l3l'), which decay predominantly to n = 2 via autoionization. Differential cross sections both for the dir ect nonresonant channel and in the vicinity of several autoionizing re sonant states are presented. The differential cross sections in the vi cinity of the autoionizing resonant states are shown to be very rich i n structure. We discuss the relevance of these calculations to a recen t experiment that measured the electron emission spectra for the colli sion of C5++H-2.