Optogalvanic Spectroscopy in Recombination-Limited Plasmas with Color Center Lasers

Abstract

Strong infrared optogalvanic signals have been observed in the region from 3600–4100 cm⁻¹ for H, He, Li, Ne, and Ar excited in hollow cathode discharges as a result of transitions induced among low Rydberg states of the atoms by a cw F-center laser. On the order of fifty transitions have been assigned in both neon and argon, eleven in helium, and one each in lithium and hydrogen. Studies of the quenching of helium and neon optogalvanic signals by the addition of hydrogen, deuterium and nitrogen to the inert gas plasmas indicate that a quasi-resonant process is occurring for the quenching of helium n = 4 → 6 transitions by H₂. The high signal-to-noise ratios observed for many of these transitions with only a few milliwatts of laser power illustrates the potential of this technique for studying excited states of atoms and molecules in plasma environments and suggests the use of atomic Rydberg optogalvanic spectra for frequency calibration in the infrared.

This work was supported by the National Science Foundation Grant # CHE-8007042.