Hyperfine structures of atomic lanthanum at sub-Doppler resolution have been recorded using diode-laser-initiated resonance-ionization and mass-spectrometric detection. Spectra were recorded for two diode-laser-pumped transitions, ${}_{}{}^2{}_{}{}^{}\mathrm{D}_{3/2}^{}{}_{}{}^{}$${\mathrm{-}}^4$F${\mathrm{°}}_{3/2}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{D}_{5/2}^{}{}_{}{}^{}$${\mathrm{-}}^4$F${\mathrm{°}}_{3/2}$, at 753.9 and 819.0 nm, respectively. The linewidths observed were as narrow as 165 MHz, substantially below the expected Doppler width of 1 GHz for the 1700-K sample. Atomic hyperfine structure constants for the 13 13260-${\mathrm{cm}}^{\mathrm{-}1}$ ${}_{}{}^4{}_{}{}^{}\mathrm{°}_{3/2}^{}{}_{}{}^{}$ state were determined from the spectra: A=-350±4 MHz and B=54±12 MHz. Isotopically selective resonance ionization was achieved, even though a broadband dye laser was involved in the overall ionization process.

• Received 16 August 1989

DOI:https://doi.org/10.1103/PhysRevA.41.2566