Projectile dependence of single-excitation cross sections at intermediate velocities.

We study 1s→2s(2p) excitation of hydrogen as a function of the nuclear charge of the projectile, ZP , for a fixed impact velocity, v51.3 a.u., for which electron excitation, capture, and ionization are competitive processes. For this purpose, we have performed large ab initio close-coupling calculations using a molecular basis in the framework of the impact-parameter method. Excitation probabilities do not saturate when ZP increases indefinitely, in agreement with recent work of Janev and with theoretical evidence on the behavior of transition probabilities at high impact energies.