Doppler-Free Intermodulated Optogalvanic Spectroscopy

Abstract

Intermodulated optogalvanic spectroscopy, a new method of Doppler-free saturation spectroscopy, is described. Preliminary values of 725±4 MHz for the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ $3{}_{}{}^3{}_{}{}^{}D_2^{}{}_{}{}^{}(F=\frac{3}{2})-3\mathrm{}{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}(F=\frac{1}{2})$ hyperfine splitting, and of 5830±6 MHz for the $3{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}(F=\frac{1}{2})-3\mathrm{}{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}(F=\frac{3}{2})$ hyperfine splitting obtained using this method are reported. Intermodulated optogalvanic spectroscopy is limited in sensitivity only by shot noise in the direct current sustaining the discharge, and compares favorably in sensitivity with other Doppler-free methods.