Transitions between triplet Rydberg states of the alkaline-earth-metal atoms for precision measurements of microwave fields

We calculated the frequencies and amplitudes of the microwave (µw) dipole transitions between triplet Rydberg states of n 3 S 1 , n 3 P 1 , n 3 D 2 , and n 3 F 3 series in the alkaline-earth atoms. Numerical values of the amplitudes determine the µw electric-field-dependent Rabi frequency of the Rydberg level shift in the field of a resonance radiation. This shift, observed as splitting of resonance in electromagnetically induced transparency for intensely absorbed probe radiation, enables measuring the µw electric field strength. For numerical calculations, we used single-electron methods and the most reliable data on quantum defect values from the literature. We derived the asymptotic approximation formulas of the µw frequencies and amplitudes.