Abstract

Resonance ionization mass spectrometry (RIMS) is recognized as an extremely sensitive and selective method of atomic detection. The use of continuous lasers offers two distinct advantages over pulsed lasers for RIMS studies. The continuous duty cycle permits higher ion yields without space-charge effects and, therefore, often gives better sensitivity. In our experiments, two counterpropagating single-frequency cw dye lasers are used to populate a highly excited state which is then ionized by the absorption of a photon from either a 100-W cw NdrYAG or a 50-W CO₂ laser. The two- photon excitation to the Rydberg state is resonantly enhanced by tuning the first dye laser to (or near) one of the atomic resonance lines. Thus far, we have observed ionization efficiencies of a few tenths of a percent using short-lived upper states. In planned experiments, which should be completed by the time of this meeting, using high Rydberg states (n ≥ 20) and a cw CO₂ laser for ionization, we expect efficiencies to approach unity due to the increased lifetime of the higher state and the increased IR photon flux.

© 1986 Optical Society of America