Near-UV sub-Doppler spectroscopy on a metastable Mg beam by a frequency-doubled diode laser

Near-UV radiation is generated by doubling the frequency of a semiconductor laser in a nonlinear crystal. The crystal is contained in a resonant cavity in order to improve the conversion efficiency. The cavity increases the efficiency by about three orders of magnitude. This radiation has been used to perform spectroscopy of metastable magnesium in an atomic beam. We observed the (3s3p)3P-(3s3d)3D transition multiplet, which is of interest for metrological applications. The isotopic shift between 24Mg and 26Mg was measured and new information on the hyperfine structure of 25Mg was obtained. This radiation source is promising also in order to improve the Mg frequency standard. (orig.)