Optical spin orientation in ruby by Zeeman-selective U-band absorption

Optically induced magnetization in ruby at room temperature has been observed by excitation of the U-absorption band. Optically induced Zeeman coherence associated with different pairs of Zeeman sublevels has also been observed as free induction decay signals. Zeeman-selectivity in the U-band transition is derived by assuming a spin-orbit coupling which provides a small fraction of the intensity of the U-band. Calculation of the relative transition probability yields different Zeeman population distributions depending on the types of irreducible representations used for the spin-orbit coupling.