High-resolution studies on bound odd-parity Rydberg states in Ba I

A study of the detailed structure of the bound odd-parity Rydberg states of barium has been undertaken using a cw dye laser in combination with an atomic beam. Special attention has been paid to the $6snf$ configurations, of which the hyperfine structure has been analyzed in terms of a small set of parameters. In addition to an effective Slater-exchange integral, an effective spin-orbit interaction, and a contact hyperfine parameter, a new parameter representing two-body magnetic effects, has been introduced. The introduction of this new parameter is discussed in some detail. Good agreement between the calculated and experimental hyperfine energies is achieved in this way.