Double resonance, fluorescence spectroscopy, and hyperfine structure in Pr I

Laser-fluorescence spectroscopy and the laser-rf double-resonance method are combined to classify lines in the Pr I absorption spectrum. The double-resonance technique is found to be particularly valuable for this purpose since, by focusing on the lower level of a transition, it leads in many cases to unique line assignments. Precise (approx.1 ppm) measurements are reported for the hyperfine-structure (hfs) constants of 15 low levels, and 0.5% values for 34 higher levels. Classifications are given for many lines in the region 5746 <lambda<6148 A. Preliminary values are derived from the double-resonance data for the single-electron hfs integrals a/sub 4f/, a/sub 5d/, a/sub 6s/, b/sub 4f/, and b/sub 5d/ for the low-electron configurations of Pr I