ELECTRIC-FIELD MEASUREMENTS IN DISCHARGES BY DOPPLER-FREE 2-PHOTON LASER STARK SPECTROSCOPY OF ATOMIC-HYDROGEN

We show experimentally that the Doppler-free, two-photon excitation of n = 3 states of atomic hydrogen using a tunable, narrow band laser so urce at 205 nm, can be used to measure the electric field in the sheat h of a low pressure glow discharge with good sensitivity (50 V/cm). Th e observed excitation spectra show a well-resolved Stark structure in good agreement with simulated spectra calculated for different values of the electric field. This method is promising for measuring the elec tric field magnitude in a number of environments because of the large laser induced fluorescence yield per ground state H atom.