State-selective electron-capture measurements for N4+-H and N4+-H-2 collisions

State-selective electron-capture cross-section measurements in the energy range between 1 and 4 keV/amu are reported for collisions between N4+ ions and atomic and molecular hydrogen. The cross sections are measured in a crossed-beam experiment by means of photon emission spectroscopy. The singlet and triplet states are resolved. It is found that the capture probabilities are not statistically distributed over both spin states and depend strongly on the primary energy. For collisions with atomic hydrogen the agreement with fully quantum-mechanical calculations is in general good. The sums of the experimental results for capture into all the singlet and triplet states are in excellent agreement with previous total one-electron capture measurements. Additionally for molecular hydrogen we performed multichannel Landau-Zener calculations that are found to be in fair agreement with the experimental data except for the highest angular momenta states. [S1050-2947(98)00701-X]