State-selective single- and double-electron capture in collisions of ${\mathrm{N}}^{4+}$ ions with He atoms have been studied at projectile energies in the range of 20–80 keV. The state-selective single- and double-electron capture cross sections and projectile scattering angle distributions were obtained using cold-target recoil-ion momentum spectroscopy. For single-electron capture, the experimentally obtained state-selective cross sections show an obvious discrepancy with the calculated results by molecular orbital close-coupling methods and are in good agreement at a projectile energy of 20 keV with other experiments. The angular distributions are compared with calculations from the multichannel Landau-Zener model. For double-electron capture, electrons captured into $2l2l^{\prime }$ states of the ${\mathrm{N}}^{4+}$ projectile are dominant. The angular distributions are explained by a two-step model combining the classical deflection function.

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• Atomic & molecular collisions