Differential excitation studies of quasi-one-electron systems

The impact parameter dependence of the BeII 22S-22P emission probability and polarisation has been studied for 1.5-15 keV Be+-HE, Ne, Ar collisions by detection of photons in two directions perpendicular to the incident beam, one orthogonal to and one in the scattering plane, in coincidence with ions scattered through a selected angle theta. The studied range of reduced scattering angles tau=Etheta corresponds to impact parameters b in a range of 0.3-1.7 au for helium, 0.5-2.2 au for neon and 1.2-2.3 au for argon. The experimental results are compared with theoretical predictions obtained by Nielsen and Dahler (J. Phys. B.; 13: 2435(1980)). (author)