High resolution laser fluorescence spectroscopy in the deep blue spectral region

High-resolution laser spectroscopy measurements have been performed in the wavelength region around 4000 Å using a pulsed dye laser acting on a collimated atomic beam. Extra-cavity Fabry-Pérot filtering was used to achieve a narrow line-width of the laser light. Isotope shifts were measured in the 4216 Å and 4202 Å rubidium lines with the result ?s(87, 85)=124.3(4)MHz, and?s(87, 85) = 124.2(7)MHz, respectively, and in the 3988 Å ytterbium line with the resultds(176, 174)=-509(4)MHz, ?s(174, 172)=-530(4) MHz.