Quantum jumps due solely to spontaneous Raman scattering between the Zeeman sublevels of a single ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}_{}^{+}{}_{}{}^{}$ ion have been observed in the fluorescence emitted by the ion. A theory of quantum jumps for this system predicts that coherences between excited levels cause the ratio of the mean duration of the "fluorescence-on periods" to the mean duration of the "fluorescence-off periods" to be independent of laser intensity. The measured value agrees with the predicted one to within the measurement precision of 2%. The distribution of the durations of the off periods also agrees with theory.

• Received 16 November 1987

DOI:https://doi.org/10.1103/PhysRevA.37.4544