Experimental cross sections for electron excitation of the 2s S-2 -> 2p P-2 transition in C3+

Experimental cross sections are reported for electron excitation of the all owed 2s S-2 --> 2p P-2 transition in C3-. Center-of-mass energies an from b elow threshold (7.00 eV). through threshold (8.00 eV), and up to approximat ely 1.5 times the threshold (12 eV). The present results an found to overla p earlier energy-loss data reported to energies oi 8.45 eV. The data are al so compared with other optical-emission results for this dipole-allowed tra nsition and with several theoretical calculations. An ''electronic aperture '' is described that allows discrimination against elastically scattered el ectrons, with their larger Larmor radii, in experiments with magnetically c onfined ions or electrons. [S1050-2947(99) 10202-6].