Effect of optical saturation on hyperfine intensities in optogalvanic spectroscopy

The hyperfine structure of the 22 125-cm/sup -1/, /sup 2/D/sup degree//sub 3/2/ reverse arrow /sup 2/D/sub 3/2/ lutetium transition has been examined by both Fourier transform emission and laser optogalvanic spectroscopy. The component intensities of the Fourier-transform spectrum closely agree with classical intensities. The optogalvanic spectra show progressively larger deviations from classical intensities as the laser power is increased. Introduction of a single optical saturation parameter into the intensity formula is sufficient to fit the observed intensities even at high laser powers. These spectra were used to derive accurate values for the /sup 175/Lu line origin, the upper-state hyperfine constants of /sup 175/ Lu, and the isotope shift between /sup 176/Lu and /sup 175/ Lu.