CW ultraviolet saturation spectroscopy of the 6p 3P0-9s 3S1 transition in mercury at 246.5 nm

We have measured the even isotope structure of the 6p ³P₀-9s ³S₁ transition in mercury at 246.5 nm using saturated absorption spectroscopy with radiation produced as the sum frequency of a 363.8 nm argon ion laser and an LD700 ring dye laser in ADP. This is the first use of cw sum-frequency mixing in nonlinear laser spectroscopy in the ultraviolet. No previous cw Doppler-free measurements have been reported at wavelenghts below 294.5 nm