Semiquantal treatment of excited-atom--excited-atom collisions

The semiquantal treatment of collision processes such as H(nl) + H(n0l0) → H(n'l') + H+ + e is described. The associated cross sections display systematic trends in the distribution over final angular momentum states in keeping with those previously predicted for e-H(nl) inelastic collisions. Deexcitation between close-neighboring levels n and n' of the projectile (with simultaneous ionization of the target) is generally more rapid than the endothermic processes involving the reverse transition in the projectile and, as n is increased, becomes quite competitive with those processes associated with no internal-energy change in the projectile, particularly at the lower impact energies. The cross sections, with appropriate statistical weights, for forward and reverse transitions in the projectile tend to the same high-energy limit