Carbon Dioxide Laser Saturation Spectroscopy at kHz Linewidths

Abstract

Consideration is given to factors limiting the resolution in laser saturation experiments. At linewidths in the range 100 kHz to 1 MHz the most important factors arise from the residence time of the absorbing molecule within the radiation field and from saturation broadening. These problems are circumvented by using beams of large diameters and low powers. Two experiments yielding spectra at linewidths around 20 kHz (full-width half-maximum) are described in outline, each employing a CO₂ laser beam of diameter several centimetres. In one experiment 10 µm saturation spectra are obtained directly using an etalon technique; in the other radio-frequency transitions are obtained in a double-resonance experiment.