Electron capture from elliptic Rydberg states: impact perpendicular to theminor axis

The total cross section, sigma, for electron capture by Na+ ions from orien ted coherent elliptic states (CES) of Li with principal quantum number n = 25 was studied experimentally for impact perpendicular to the minor axis of the elliptic orbit. The remaining geometrical parameters of the CES, which are the eccentricity, e, and the angle, phi, between the major axis and th e beam direction, were varied in the course of the experiments, as was the reduced impact velocity upsilon(r) = n upsilon, where upsilon is the projec tile velocity in atomic units. Several representative cuts were chosen with in the parameter space (upsilon(r), e, phi) = (0.74-2.09, 0-1, 0-2 pi). The velocity range includes the region of matching velocities (upsilon(r) simi lar or equal to I) where a for given geometrical parameters attains its max imum value and the high-velocity region where a is a strongly decreasing fu nction of upsilon(r). The cross section depends sensitively on each geometr ical parameter and the dependences change dramatically as upsilon, is varie d. The spatial distribution of the CES apparently governs sigma in some reg ion of parameter space (upsilon(r), e, phi) and in another the momentum dis tribution prevails.