FAST INELASTIC ION-ION, ION-ELECTRON, AND ION-POSITRON COLLISIONS

We present scaling relations for the total cross sections and collisio n strengths of bound-state excitation in positive ions. The colliding particle can be positively or negatively charged and can be a fully io nized atom, an electron, or a positron. We consider collisions in whic h the kinetic energy of relative motion is large and consequently the adiabaticity parameter xi much less than 1. We illustrate our general method by calculating collision strengths for proton-impact excitation of fine-structure transitions in hydrogenlike ions. The limiting case of infinite nuclear charge is also included in our calculations. Usin g a unitarized Coulomb-Born approximation, we show that, for dipole tr ansitions, colliding particles with large orbital angular momenta (l g reater than or similar to 2000) make an important contribution (approx imately 70%) to the collision strength of proton-impact excitation. Fo r a nonrelativistic projectile energy E(i) --> infinity, we use the Bo rn approximation to obtain the scaled collision strengths. These limit ing values, dependent only on the particular transition, confirm the c orrect high-energy behavior of our data. We also use the interactive g raphics computer program OMEUPS [Burgess and Tully, Astron. Astrophys. 254, 436 (1992)] to extrapolate our data to higher energies.