New high-resolution study of the 6s subshell spectrum of Tl I

The authors report new high-resolution measurements of the 6s subshell photoabsorption spectrum of Tl I. The observations were made in the first order of a 6000 line/mm holographic grating of 3 m radius, using synchrotron radiation as the background source of continuum. All the series are extended to higher n values, and the earlier analysis is improved. A two-dimensional analysis by multichannel quantum defect theory reveals two prominent perturbations due to coupling between series converging to the 3 P 0 and 1 P 1 limits and between series converging to the 3 P 2 and 1 P 1 limits.