Measuring the electric field strength of microwave radiation at the frequency of the radiation transition between Rydberg states of atoms $^{85}$Rb

The spectral characteristics of the resonance effect of the electromagnetic-induced transparency (EIT) of rubidium atomic vapors induced by intense radiation with a wavelength in the region from 479 to 486 nm in the presence of microwave radiation at a frequency of 1 to 300 GHz, which splits the energy of transition of the atom from the resonant 5$P_{3/2}$ states into the Rydberg $nD_{5/2}$ state, are determined. The magnitude of the splitting of the EIT peak is proportional to the electric field intensity of the microwave radiation. Simple approximation expressions are obtained for the numerical calculation of the transition amplitude between Rydberg $nD_{5/2}$ and $(n+1)P_{3/2}$ states with large principal quantum numbers $n$. A setup has been developed for measuring the electric field intensity of microwave radiation based on measuring the frequency of splitting of the resonance of an electron microscope in the absorption spectrum of probe radiation.