IODINE HYPERFINE STRUCTURE OBSERVED IN SATURATED ABSORPTION AT 633 nm

Abstract

Hyperfine components of the R(127) line of the 11–5 band of molecular iodine at 633 nm have been observed by saturating the absorption inside the cavity of a single‐frequency He–Ne laser. The component widths of 4.5 MHz were broadened a factor of 2 by 1‐Torr iodine pressure, or by 500‐G magnetic field. Since no wavelength shift as large as 2 MHz was observed, wavelength perturbations from these sources should be controllable to less than 2 × 10⁻¹³λ. The use of one of these components as a reference for laser stabilization is suggested.