Ionization of Rydberg atoms of sodium by 360-4400 eV alkali-metal ions

Impact ionization by singly charged ions from Rydberg Na(24d) and Na(25s) s tates has been investigated over the reduced velocity region <(upsilon)over tilde> = 0.5-2.2. The ions of Na+, K+, and Li+ were accelerated to energie s from 360 to 4400 eV and used to bombard the laser-excited Rydberg atoms. Electrons released in the ionization of Rydberg atoms were collected from t he collision Volume and registered by a channel electron multiplier. Measur ed relative ionization cross sections from Na(24d) and Na(25s) states show maxima at <(upsilon)over tilde> = 1.6-1.7 and agree moderately well with cl assical-trajectory Monte Carlo calculations. [S1050-2947(99)03709-9].