LASER-INDUCED LINE NARROWING IN 3-LEVEL SYSTEMS - APPLICATION TO THE DETERMINATION OF THE WAVENUMBER OF THE 3S2-2P4 NEON LINE (LAMBDA=6328-A)

The Doppler-free absorption line narrowing technique (A.L.N.) is applied to the 20Ne (3s2-2p4-1s5) three-level system, using a 127I2 stabilized He-Ne laser (λ = 6328 Å) and a tunable single-frequency cw dye laser (λ = 5945 Å). The relative frequency positions of the 20Ne 3s2-2p4 line and of some iodine hyperfine components are measured with an uncertainty of 1 MHz. The wavenumber of the 20Ne line at low pressure (0.2 Torr) is deduced from these measurements and is found to be σ(20Ne, 3s2-2p4) = 1579800.060 ± 0.005 m-1. With regard to the previous results, the accuracy is increased by two orders of magnitude. © 1979.