Abstract

Hyperfine structure measurement by a high-resolution laser spectroscopic method based on optical phase conjugation by nonlinear wave mixing is presented by using different atomizers, including analytical flames and low-pressure dc discharge plasmas. Isotope solutions can be conveniently introduced to a flame atomizer such as an air-acetylene flame. When a demountable discharge plasma atomizer (1–10 Torr) is used, pressure broadening is also minimized and Doppler broadening is cancelled. Unlike many other nonlinear methods, these Doppler-free nonlinear wave mixing methods (e.g., degenerate four-wave mixing) offer easy optical alignment and excellent detection sensitivity (parts-per-billion or better) and require very low laser power levels (e.g., nanojoules for excimer-pumped or Nd:YAG-pumped dye lasers). One can also use low-power cw lasers such as argon-ion-pumped single-frequency ring dye lasers. Theoretical isotope/hyperfine-structure profiles can be calculated by using simple quadratic Lorentzian profiles and can then be matched with the experimental spectra for many elements such as Ba, Ca, Na, Mn, and Li. By using “transient” coherent-grating based signal generated by vectorial optical phase conjugation, certain lines of a fine structure could be selectively probed, and hence, simpler Doppler-free fine structures could be measured.

© 1992 Optical Society of America