Doppler-free spectroscopy in a hollow-cathode discharge: Isotope-shift measurements in molybdenum

The isotopes shifts of nine molybdenum lines between the levels $\left(4\mathrm{}{d}^{4}5s^2\right)a{}_{}{}^5{}_{}{}^{}D-\left(4\mathrm{}{d}^{5}5p\right)z{}_{}{}^5{}_{}{}^{}P$ have been studied in a newly developed hollow-cathode discharge tube with Doppler-free intermodulated fluorescence and optogalvanic spectroscopy. A homogeneous linewidth of 25 MHz is observed. The isotope shifts are determined with an accuracy of 2 MHz. This is an improvement of approximately one order of magnitude compared to previous measurements. Our results for the isotope shifts agree with previous results of Doppler-limited measurements within the error limits.