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 semicond uctor laser in a nonlinear crystal. The crystal is contained in a reso nant cavity in order to improve the conversion efficiency. The cavity increases the efficiency by about three orders of magnitude. This radi ation has been used to perform spectroscopy of metastable magnesium in an atomic beam. We observed the (3s3p)3P-(3s3d)3D transition multiple t, which is of interest for metrological applications. The isotopic sh ift between Mg-24 and Mg-26 was measured and new information on the hy perfine structure of Mg-25 was obtained. This radiation source is prom ising also in order to improve the Mg frequency standard.