Using experimental measurements of three-level avoided crossings to determine the quantum defect for the Stark map of highly excited cesium Rydberg atoms

摘要

The spectra of Rydberg atoms in the domain of three-level avoided crossings formed by the Rydberg 49S(1/2) state and high-l states in the n = 45 manifold are observed in the standard magneto-optical trap of cesium. We develop a highly accurate method which uses the spectroscopic results in order to refine the quantum defect of the 49S(1/2) state from the previous value 4.0495 +/- 0.0001 extrapolated from n = 6-30 S states [K. H. Weber and C. J. Sansonetti, Phys. Rev. A 35, 4650 (1987)] to the new value 4.049 78 +/- 0.000 03. For this purpose, we determine two characteristic properties of the avoided crossings: (i) the minimum gap between the upper and the lower levels, and (ii) the value of equal gaps between the upper and the middle levels and between the middle and the lower levels. The experimental results for the avoided crossing near 4 V/cm are (i) (111.7 +/- 1.3)h MHz, and (ii) (57.0 +/- 2.1)h MHz. For comparison, quantum mechanical simulations based on the published quantum defect yield (i) 109.52h MHz, and (ii) 56.04h MHz. The refined quantum defect is adjusted such that it yields (i) 111.50h MHz, and (ii) 56.98h MHz, in even better agreement with the experimental results. The theoretical values of the electric fields for (i) and (ii) differ by 0.03 V/cm, in perfect agreement with the experimental results. The refinement also improves the agreement of their absolute values. The remaining similar to 1.5% difference is attributed to effects of stray fields.