Charge Changing Collisions of Atomic Beams in Alkali-Metal Vapors. I. Formation of H-, C-, O- and S- Ions

Abstract

Charge changing collisions leading to negative ion formation have been studied for H + , C + , O + and S + ion beams passing through vapors of Cs, K and Na. Collision cell method is used, and the energy range studied is from 0.5 keV to 5.0 keV. Fractions of outgoing particles in three charge states 1, 0 and -1 have been determined as a function of target atom thickness \(\varPi\) (atoms/cm 2 ). Except the hydrogen case, the fractions of negative ions at very thick targets are as high as 53 to 95% of the total beam. The maximum conversion coefficients of primary positive ions into negative ions have also been determined. The result shows that except the hydrogen case, cesium is the most efficient target in the energy range studied and converts 29% of C + ions, 24% of O + ions and 15% of S + ions into negative ions at the optimum energies and \(\varPi\) values.