Nuclear Orientation ofCadmium111by Optical Pumping with the Resonance Line5S01−5P11

Abstract

Nuclear orientation by optical pumping of a diamagnetic ground state can only be performed efficiently if the hyperfine structure of the excited state is at least of the order of magnitude of its natural width. Furthermore, the efficiency of such a nuclear orientation varies very much with the intensity of the applied magnetic field. In a field high enough to decouple totally the hyperfine structure of the excited state, this efficiency tends to zero. Several new effects which were predicted in such situations have been experimentally verified in the case of cadmium 111, the $I=\frac{1}{2}$ nuclear spin of which being oriented by optical pumping by the $5^{1}S_{0}\ensuremath{-}5^{1}P_{1}$ resonance line at 2288 \AA{}. Indeed, the $5^{1}P_{1}$ level has a hyperfine structure which is of the same order of magnitude as its natural width.Among these new effects is an interesting possibility of optical pumping of a spin \textonehalf{} without the use of a polarizer for intermediate values of the magnetic field, and a shift of the nuclear magnetic resonance in the ground state due to "hyperfine coherences" existing in the excited state. The sign of the hyperfine structure of the $5^{1}P_{1}$ level of cadmium 111, previously unknown is experimentally measured and found positive and several new methods are proposed to measure very small hyperfine structures. The situation discussed here is closely related to what is known as "anticrossing" of energy levels.