Use of atomic-beam laser radio-frequency double resonance for interpretation of complex spectra: Tb i as a test case

The usefulness of the atomic-beam laser-rf double-resonance technique as an aid in the interpretation of complex optical spectra is investigated. A 2-A-wide region (centered on 5441 A) in the spectrum of Tb i is selected for the test. Some 25 atomic lines, many with severely overlapping hyperfine structure (hfs) patterns, had been observed in the region, and only a few of these had been successfully classified. The procedure followed for each line was to measure the hfs intervals of the lower level precisely and then to compare them with the known intervals of previously designated low levels. The procedure leads to a successful identification for only about half of the levels studied, owing principally to the small size of the ensemble of levels with known splittings. The method does have advantages, however, and is shown to be a useful supplement to conventional spectroscopic techniques. A number of new line classifications, level designations, and hfs intervals are reported