Absolute optical frequency measurement of saturated absorption lines in Rb near 422 nm

We present absolute optical frequency measurements of the 5s(2)S(1/2)-6p(2)P(1/2) hyperfine resolved transitions in both (85)Rb and (87)Rb near 422 nm. The frequency of each transition was measured by stabilizing a narrow-linewidth extended cavity diode laser to the transition under study and by measuring that frequency with a femtosecond laser frequency comb. A frequency-doubled 844 nm laser was used as a frequency link to connect the 422 nm probe laser to the near infrared part of the comb. The resulting uncertainties of < 70 kHz in the Rb transition frequencies represent a four-order of magnitude improvement over previously published results. The frequencies reported in this paper are one of the most accurate series of measurements made in the violet region of the spectrum.