Optogalvanic spectroscopy using 389 nm coherent light source accurately tuned to resonance frequency of 2S->3P of He

An efficient 389 nm coherent light source, made possible through the single-pass second-harmonic generation of a picosecond Ti:sapphire laser with a periodically poled lithium niobate waveguide, was developed for the metastability exchange optical pumping of hyperpolarized ³He gas, which is applicable to imaging with nuclear magnetic resonance. The second-harmonic light provided such a broad spectrum that some split sub-levels of its metastable state under an applied magnetic field could be pumped efficiently and simultaneously. Optogalvanic spectroscopy using the light source indicated that the spectral width of ³He was much less than 70 GHz, which was similar to the spectral width of the light source.