Atomic & Molecular Spectroscopy by Saturation with Coherent Light
For many studies in the interaction of light with matter, we need sources of powerful, coherent, monochromatic light tunable to the wavelengths absorbed by simple atoms and molecules. Gas lasers, although limited to a few discrete lines with a limited tunability across each, have been used in the Hänsch-Borde modulation method of saturation spectroscopy to study hyperfine structures of a number of iodine lines (Levenson, Sorem and Hänsch). Recently Sorem has extended this work to investigate the Zeeman effect. Also, a new method of intermodulated fluorescence permits us to use saturation narrowing at pressures so low that collision effects are negligible. Lines as narrow as 3 Mhz (one part in 2×108) have been observed.