Precision Measurement of the Excited State Lande g-factor and Diamagnetic Shift of the Cesium D2 Line

Transitions between the extreme angular-momentum states of alkali D lines hold the potential for enabling accurate high-field optical magnetometry because of their very simple magnetic field dependence described only by a linear and a quadratic term, characterized by the two coefficients & gamma;1 and & gamma;2. Here, we present very accurate measurements of these coefficients, for the cesium D2 line, thereby overcoming a major obstacle for the realization of this future technology. By means of saturated absorption spectroscopy on a cesium gas, in 3 T and 7 T magnetic fields, we measure the linear magnetic frequency shift of the transition to be & gamma;1 = 13.994 301(11) GHz/T. This measurement corresponds to an optical magnetic field determination of better than 1 ppm accuracy. From this value, we can calculate the fine-structure ode & PRIME;g-factor gJ(62P3/2) = 1.334 087 49(52). This result is consistent with the previous best measurement, and it improves the accuracy by more than 2 orders of magnitude. We also measure, for the first time, the quadratic diamagnetic shift as & gamma;2 = 0.4644(35) MHz/T2. Our work opens up the field of accurate high-field optical magnetometry using atomic cesium, with possible applications in, e.g., medical MRI, fusion reactors, and particle accelerators. These high-accuracy measurements also allow for testing of advanced atomic structure models, as our results are incompatible with the Russel-Saunders coupling value and the hydrogen-constant-core-model value by 31 and 7 standard deviations, respectively.

Automated summary

By accurately measuring the transitions between extreme angular-momentum states of the cesium D2 line, we have overcome a major obstacle for accurate high-field optical magnetometry. We obtained very precise measurements of the linear and quadratic magnetic field dependence, characterized by the coefficients γ1 and γ2, which have potential applications in medical MRI, fusion reactors, and particle accelerators.