Measurement of hyperfine coupling constants in the 3dt2Dj levels of K39, K40, and K41 by polarization quantum-beat spectroscopy
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Hyperfine quantum-beat spectroscopy has been utilized in a pump-probe configuration to measure magnetic dipole (A) and electric quadrupole (B) coupling constants in the 3d[Formula Presented] and 3d[Formula Presented] levels of three isotopes of potassium. For many of these levels, the largest hyperfine splitting is smaller than the natural width, and so a subnatural linewidth technique is required. In the experiments, the 3d levels are excited on the 4d[Formula Presented]3d[Formula Presented] quadrupole transition with linearly polarized light. Time evolution of the alignment components in the d levels is probed by time-delayed resonant radiation on the 3d[Formula Presented]9p[Formula Presented] transitions. Comparison of the excitation rate for two orthogonal relative polarization directions of the pump and probe laser at each delay time permits derivation of a linear polarization degree. This quantity contains beats at the various hyperfine frequencies in the d levels. Fitting the experimentally obtained time dependence to theoretical expressions allows extraction of the hyperfine coupling constants. For the 3d[Formula Presented] level of [Formula Presented] we obtain A=0.96(4) MHz and B=0.37(8) MHz, indicating a typical precision also obtained for the other levels and isotopes. 1997 The American Physical Society.