Electric field induced hyperfine level-crossings in (nD)Cs at two-step laser excitation: Experiment and theory

The pure electric field level-crossing of m_F Zeeman sublevels of hyperfine F levels at two-step laser excitation is described theoretically and studied experimentally for the nD_3/2 states in Cs with n = 7, 9 and 10, by applying a diode laser in the first 6S_1/2 → 6P_3/2 step and a diode or dye laser for the second 6P_3/2 → nD_3/2 step. Level-crossing resonance signals are observed in the nD_3/2 → 6P_1/2 fluorescence. A theoretical model is presented to describe quantitatively the resonance signals by correlation analysis of the optical Bloch equations in the case when an atom simultaneously interacts with two laser fields in the presence of an external dc electric field. The simulations describe well the experimental signals. The tensor polarizabilities α₂ (in ) are determined to be 7.45(20) × 10⁴ for the 7D_3/2 state and 1.183(35) × 10⁶ for the 9D_3/2 state; the electric field calibration is based on measurements of the 10D_3/2 state, for which α₂ is well established. The α₂ value for the 7D_3/2 state differs by ca. 15% from the existing experimentally measured value.