The 5dnf J=4 and 5 autoionising Rydberg series in barium: experiment and MQDT analysis

Abstract
Accurate values for the energies and linewidths of the 5dnf J=5, 4 (n=4-50) autoionising Rydberg series of neutral barium have been collected using either a single-mode CW ring dye laser or a Nd:YAG pumped pulsed dye laser and a beam of neutral atoms in the metastable 5d2 1G4 and 5d2 3F states. The interactions between series within the configuration converging to the 5d3/2 and 5d5/2 ionisation limits as well as the continuum interactions (for J=5) have been analysed using multichannel quantum defect theory (MQDT) in the 'phaseshifted reaction matrix' formalism. Good agreement between experiment and MQDT calculations is obtained; however, not all interaction parameters could be determined from the available data.