Observation by two-photon laser spectroscopy of the 4d105s 2S1/2→4d95s22D5/2 clock transition in atomic silver

We report the observation of the very narrow 4d105s 2S1/2→4d95s22D5/2 transition in atomic silver. The frequencies of the hyperfine components in 107Ag and 109Ag have been measured using Doppler-free two-photon laser spectroscopy of a thermal beam and heterodyne calibration with respect to the a1 component of the 62P(4-5) line in molecular iodine near 661 nm. For the center of gravity of a mixture of natural abundance, we deduce the value 906 641 295.77(19) MHz. For the isotope shift, we obtain ν(109Ag)-ν(107Ag)=564.15(37) MHz, from which we deduce the frequency and isotope shift of the 4d105s 2S1/2→4d106p 2P3/2 transition at 206 nm