Saturation spectroscopy and resonant degenerate four-wave mixing in Hg at 546.1 nm

All the central components of the optically-excited atomic mercury laser 546.1-nm transition have been clearly identified by means of Doppler-free saturation spectroscopy performed in an RF discharge in mercury vapor. Resonant degenerate four-wave mixing, also observed at this wavelength, is found to be of interest because it provides an atomic system easily reached by CW dye lasers, and because it does not suffer from hyperfine optical pumping for the case of even mass-number isotopes. The measured Doppler width of the individual components was 525 + or - 25 MHz, corresponding to a translational temperature of about 350 K.