Comb-Referenced Doppler-Free Spectrometry of the ^{200}Hg and ^{202}Hg Intercombination Line at 254 nm.

We report on precision spectroscopy of the 6s^{2} ^{1}S_{0}→6s6p ^{3}P_{1} intercombination line of mercury in the deep ultraviolet, by means of a frequency-comb referenced, wavelength-modulated, saturated absorption technique. This method allowed us to perform sub-Doppler investigations with an absolute frequency axis at 254 nm, while ensuring a relatively high signal-to-noise ratio. The absolute line center frequencies of the ^{200}Hg and ^{202}Hg bosonic isotopes were measured with a global uncertainty of 8 and 15 kHz (namely, 6.