Download Photoline
Akiko Fleischer
The angular distribution parameter, β, of the atomic Li 2s photoline is found to deviate significantly from expected values of β = 2.0 at some of the 1s arrow np excitations. Off resonance, the β value is found to be 2.0 as expected. For half open-subshell atoms (and all closed subshell atoms) the β value of any s-subshell electron must be 2.0 in the absence of relativistic effects. Hence, deviations of β from 2.0 are an indication of the presence of relativistic effects. That such effects should be so pronounced in such a simple atom as Li is rather surprising. A simple expression which describes the β value of the 2s photoline on resonance in terms of the ratio of the j = 1/2 to the j = 3/2 partial wave amplitudes will be presented which explains qualitatively how β can deviate from 2.0. In addition, at the 1s2s(^3S) threshold, an unexplained feature is observed in the 2s differential cross section recorded at 90^o with respect to the polarization vector of the ionizing radiation. This feature may be related to the pile-up of the 1s2s(^3S)np Rydberg series.