Fine structure of Rydberg states. IV. Completely resolved fine structure inD,F, andGstates ofHe4

Abstract

The authors have made extensive new measurements in Rydberg (n=6 --11) D, F, and G states of helium. The new data represent over 1100 individual resonance scans, totalling some 2200 h of data-collection time. In order to perform such a large number of runs, data logging has been automated by interfacing a microcomputer to an apparatus previously used to make fine-structure measurements in one- and two-electron atoms. An exhaustive analysis of possible systematic line-center shifts, including black-body radiation effects, was carried out. The root-mean-square one-standard-deviation experimental uncertainty is 294 kHz for our 67 measurements. The large quantity of new measurements has allowed us to perform a global least-squares fit to all existing state-resolved data in D, F, and G states. The complete structure of the D, F, and G manifolds is now known for n> or =6 to a precision of a few megahertz or better. Current theoretical calculations for a typical (30-GHz) interval differ from the measurements by 6 x 10/sup -8/ a.u., or over 1000 experimental standard deviations.