PUB - Publikationen an der Universität Bielefeld

We measured the total ionization asymmetry A in dependence on the incident electron energy E Here 'total' refers to integration over all emission angles and energy partitions of the outgoing electrons. From a threshold value of A = 0.1 25 the A(E) curve rises smoothly toward a broad maximum of A(max) = 0.31 at E(max) = 8.3 eV. The fall-off towards higher energies is quite similar to that of the other one-electron atoms. However, it shows a structure which can be explained by contributions from autoionizing P states. Bartschat has made a theoretical estimate of A(E) for various atoms. At low energies the agreement with our data is satisfactory, at higher energies the experimental A values are considerably smaller than the theoretical ones. In the threshold region measurements were performed with small electron energy width (0.1 eV). No structure in the A(E) curve was found. The slope at threshold was determined as dA/dE = (0.136+/-0.005) eV-1.