Measurement of absolute energy level and hyperfine structure of 87Rb 4D5/2 using double resonance optical pumping method

We have measured the absolute frequency and the uncertainty of the excited state transition, 5P_3/2-4D_5/2, in ⁸⁷Rb atom with a fs frequency comb, utilizing the double resonance optical pumping (DROP) method. The absolute energy level of 4D_5/2 state is determined by measuring the absolute frequency of the 5S_1/2-5P_3/2 transition simultaneously. The hyperfine structure constants of the 4D_5/2 state are obtained with the magnetic dipole constant uncertainty reduced ten-fold compared to the previous result and with the electric quadrupole constant determined for the first time.