Measurement of Hyperfine Coupling Constants of the 5d²D₃/₂ and 5d²D₅/₂ Levels in Atomic Cesium Using Polarization Quantum Beat Spectroscopy

Abstract

Accurate measurements of hyperfine constants have revealed effects that can not be explained by a simple hydrogenic picture of the alkali atoms such as cesium [1-3]. More precise experimental results and theoretical treatments are in demand for the alkali elements, especially for atomic cesium because of its wide range of applications. Therefore, it is essential to understand its atomic and nuclear structure. Precision measurement of its excited-states properties such as hyperfine structure provides global information on nuclear charge and current distributions and also serves as a check to the theory and a calibration of calculated excited state wave functions. Accurate wave functions are important in many applications, including the analysis of atomic parity-violation experiments [4]. I n this experiment, a pump-delayed-probe method based on quantum beat spectroscopy has been used. Cesium atoms are prepared by a short, resonant light pulse ( the pump) in a superposition of excited hyperfine levels ( 5d2D1/2 or 5d2D5/2) through an electric quadrupole transition. The system evolves in time according to the Schrodinger equation with the coherence due to the unresolved hyperfine structure in the excited states. After a certain delay time, the second pulse (the probe) probes the system from the excited states to the final state (12p2P3/2), the fluorescence from the final state to the ground state (6s2S]1/2) is monitored and polarization spectra are measured. From the measured beat frequencies the magnetic dipole coupling constant a and electric quadrupole coupling constant b are obtained : a = -21.22(1) MHz; b = 0.16(15) MHz for 5d2D5/2 level and a = 48.80(3) M H z; b = 0.12(30) MHz for 5d2D3/2 level.