Angular Momentum Transfer in Electron-Atom and Atom-Atom Collisional Ionization.

Single and double differential cross sections for ionization in e^- + H(n l) and H(1s) + H(n l) collisions are reported as a function of the impact energy E of the projectile, final energy E_{f} and angular momentum L_{f} of the ejected electron. This process is assumed to occur via an energy-changing and angular momentum-changing binary collision between the Rydberg electron in prepared state (nl) and the projectile electron e^- or H(1s). The atomic projectile can also be excited during this process. Systematic trends in the variation of the classical ionization cross sections with final angular momentum L_{f} of the ejected electron are discussed and are in accord with a previous quantal treatment, whereby the non -dipole (Deltal > 1) transitions are much more important in the low and intermediate energy range of relative motion, and that the value of the final angular momentum of the ejected electron depends mainly on the initial value of the principal quantum number n of the Rydberg atom.