Centrifugal barrier effects in the 3p spectrum of calcium

The authors report a new high-resolution study of the 3p spectrum of calcium at eight times the dispersion and resolution available to previous workers. The experiment was performed at the synchrotron radiation laboratory of the 500 MeV accelerator in Bonn. As a direct consequence of improved resolution, the analysis of the spectrum has been almost completely revised with the help of multichannel quantum defect theory. Centrifugal barrier effects are found to be responsible for a large difference in quantum defects between the singlet and triplet series. Some consequences are drawn concerning two-step autoionisation.