Measuring the hyperfine splittings and deriving the hyperfine-interaction constants of Cesium 7D 5/2 excited state

The measurement of Cesium (Cs) 7D5/2 excited state's hyperfine splitting intervals and hyperfine-interaction constants has been experimentally investigated based on ladder-type (852 nm + 698 nm) three-level Cs system (6S1/2 - 6P3/2 - 7D5/2) with room-temperature Cs atomic vapor cell. By scanning the 698-nm coupling laser's frequency, the Doppler-free high-resolution electromagnetically-induced transparency (EIT) assisted double-resonance optical pumping (DROP) spectra have been demonstrated via transmission enhancement of the locked 852-nm probe laser. The EIT-assisted DROP spectra are employed to study the hyperfine splitting intervals for the Cs 7D5/2 excited state with a room-temperature cesium atomic vapor cell, and the radio-frequency modulation sideband of a waveguide-type electro-optic phase modulator(EOPM) is introduced for frequency calibration to improve the accuracy of frequency interval measurement. The existence of EIT makes the DROP spectral linewidth much narrower, and it is very helpful to improve the spectroscopic resolution significantly. Benefiting from the higher signal-to-noise ratio (SNR) and much better resolution of the EIT-assisted DROP spectra, the hyperfine splitting intervals between the hyperfine folds of F" = 6, F" = 5, and F" = 4 of cesium 7D5/2 state HFS6"-5" = -10.60(0.17 MHz and HFS5"-4" = -8.54(0.15) MHz) have been measured, and therefore the magnetic-dipole hyperfine-interaction constant A = -1.70(0.03 MHz) and the electric-quadrupole hyperfine-interaction constant B = -0.77(0.58 MHz) have been derived for the Cs 7D5/2 state. These constants have important reference value for the improvement of precise measurement and determination of basic physical constants.