Abstract

The coupling between the Zeeman sublevels of an atom by a resonant microwave magnetic field also induces a phase coherence between the states. The effect is equivalent to the precession at the Zeeman frequency of a transverse magnetic moment about the static magnetic, and is manifest as a modulation of the circularly polarized emission at the Zeeman frequency. We have investigated such phase coherence in the ²E excited state of Cr³⁺ ions occupying sites of both cubic and tetragonal symmetry in magnesium oxide, MgO. The experiments were carried out at 1.6K, in the X-band frequency range (ν ~ 9.5 GHz) with the magnetic field parallel to the crystal [111] direction. In this orientation the optically detected magnetic resonance spectra from Cr³⁺ ions in cubic and tetragonal symmetry sites are well-separated in magnetic field. In addition all three resonances from the mutually orthogonal tetragonal species occur at the same magnetic field. The purpose of this geometry is to eliminate cross-relaxation between cubic and tetragonal sites.

© 1984 Optical Society of America