  We report the absolute frequency measurements of rubidium 5S-7S two-photon
transitions with a cw laser digitally locked to an atomic transition and
referenced to an optical frequency comb. The narrow, two-photon transition,
5S-7S (760 nm) insensitive to first order in a magnetic field, is a promising
candidate for frequency reference. The performed tests yield the transition
frequency with accuracy better than reported previously.
