Experimental angular distributions for electron capture by slowNe+q(q=3–6) ions from He

Angular distributions of product Ne ions have been measured for ${\mathrm{Ne}}^{+\mathrm{q}}$ (q=3–6) capturing electrons from He at laboratory incident energies between 172 and 1200 eV. For q=4 the distributions are strongly peaked in the forward direction, while for q=3, 5, and 6 the reaction products are concentrated at larger scattering angles. Oscillatory structure is seen for q=4 and 6. The distributions are interpreted in terms of classical defelction functions calculated using model potentials. The oscillatory structure is identified as due to Stueckelberg oscillations. On the basis of the experiment and model results, it is argued that the forward peaking for q=4 may be expected to be a general characteristic of capture by multiply charged, but not bare, projectiles which lead to the population of s orbits on the projectile core.