SCALING LAWS FOR SINGLE AND DOUBLE-ELECTRON CAPTURE IN A(Q-GREATER-THAN-OR-EQUAL-TO-Z(A)-2) AT LOW IMPACT VELOCITIES()+HE COLLISIONS (Q)

We present empirical scaling laws, as a function of the projectile cha rge state, for single and double electron capture in slow collisions b etween highly charged ions and He atoms at impact velocities of 0.1 an d 0.5 a.u. The fitting parameters are shown to be suitable for predict ing the populated states in single and double electron capture. The sc aling law for single capture is found to be nearly independent of the projectile velocity in the range 0.1-0.5 a.u. The same fitting procedu re is followed for double electron capture at the velocity of 0.5 a.u. since independent monoelectronic transitions, due to electron-nucleus interactions, are dominant. At this velocity? the scaling law for the projectile:charge dependence of double electron capture cross section s is found to be similar to that for single electron capture. At-the l ower velocity of 0.1 a.u., where dielectronic processes caused by the electron-electron interaction gain importance, the charge dependence o f double capture cross sections is strongly modified.