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 was 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 to 6P_3/2 step and a diode or dye laser for the second 6P_3/2 to nD_3/2 step. Level-crossing resonance signals were observed in the nD_3/2 to 6P_1/2 fluorescence. A theoretical model was developed 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 described well the experimental signals. The tensor polarizabilities (in Bohr radii cubed) were determined to be 7.45(20) x 10^4 for the 7D_3/2 state and 1.183(35) x 10^6 for the 9D_3/2 state; a well established tensor polarizability value for 10D_3/2 was used to calibrate the electric field. The tensor polarizability value for the 7D_3/2 state differed by ca. 15% from the existing experimentally measured value.