Strong polarization effects have been observed in optical radiation from excited $J\ensuremath{\ne}0$ states arising from low-energy
Na+ -Ne collisions. In one case where radiation originates from a
J=1 to
J=0 transition, oscillations in the excitation function are found to be due exclusively to the polarization component of the radiation perpendicular to the beam direction. These are the first experimental observations of strong sublevel-state selection associated with collisional quantum-mechanical phase-interference phenomena.
New experimental results have been obtained in collisions of singly charged ions with Na Rydberg atoms. (a) The distribution of final n states populated by electron capture shows non-monotonic variations of width with incident energy over the range 60-2100 eV. (b) The total capture cross section for alkali ions on Rydberg targets shows peaks and dips over the same energy range, correlated with particular reduced velocities v and the polarization of the exciting laser. (c) {ell}-Changing collision of Na{sup +} on Na(nd) targets, n=26 and 28, at low v preferentially transfer multiple units {h_bar} of orbital angular momentum under single-collision conditions, despite very large impact parameters. (d) Inelastic impacts of Na{sup f+} on Na 36s and 30p states, perturbed by electric fields, populate a strongly field-dependent mixture of nearby Stark levels. A synopsis of recent progress will be given.
We present a time-dependent method to investigate the mass polarization effect on the resonant energies of $\overline{p}\ensuremath{-}{\text{He}}^{+}$ and the state-specified protonium formation in low-energy antiproton--hydrogen-atom collisions in Jacobi coordinates. Comparing with our previous calculations in the
V-shaped coordinates by neglecting the mass polarization, we confirm that the mass polarization effect on the protonium formation is negligibly small. We also calculated the resonant energies of $\overline{p}\ensuremath{-}{\text{He}}^{+}$ in the
V coordinates and Jacobi coordinates. The differences of the resonant energies between the two calculations are less than 4 meV. This also confirms that the mass polarization effect is negligibly small even in the resonant region.