Investigation of the C3+ Auger KLL spectrum obtained in collisions of 6-15 MeV C4+ (1s2, 1s2s 3S) with gas targets

Single electron transfer to the 1s2s  3 S long-lived component of the naturally occurring mixed-state (1s 2 , 1s2s  3 S) C 4+ ion beam in collisions with gas targets was investigated using zero-degree Auger projectile spectroscopy at  the Demokritos 5.5 MV  t andem accelerator . The observed KLL Auger spectrum contains 1s2s2p  2 P and  4 P states resulting from direct 2p transfer to the 1s2s  3 S. Higher lying (1s2s  3 S)nl 2,4 L states produced by nl transfer (n>2) were also observed and can in principle feed the lower lying  1s2s2p 2 Pand  4 Pstates. However, due to spin selection rules only the quartets have large enough radiative branching ratios resulting in a proposed selective feeding of only the 1s2s2p  4 P state by E1 cascades, while minimally affecting the 1s2s2p  2 P states. In the absence of cascades, the ratio of cross sections for 2p transfer to the 1s2s  3 S state, R m ≡  σ m ( 4 P)/ σ m ( 2 P), is 2 according to spin statistics. However, the 1s 2 ground state beam component also contributes to the production of the 1s2s2p  2 P doublet states by transfer-excitation. To isolate just the 1s2s  3 S transfer contribution and compute R m , a new technique was employed requiring the recording of two KLL spectra, with the same collision energy, but each with appreciably different 1s2s  3 S content, varied by stripping techniques. Our determination of R m shows this to be  > 2, in agreement with spin statistics, but contrary to the expected  4 P enhancement due to cascade feeding. Details of the analysis and results are discussed.