Measuring The Hyperfine Splitting And Deriving The Hyperfine Interaction Constants Of Cesium 7D_5/2 Excited State

The measurement of the hyperfine structure of alkali metal atoms has been a topic of concern.For the hyperfine structure of S state and P state,the experimental results are consistent with the theoretical prediction.However,due to the strong correlation effects and shielding effects,the measurement of hyperfine structure of D state is a great challenge.Owing to the excitation of alkali metal atoms from S state to D state cannot be realized by the single photon transition from the ground state,it can be realized by the two-photon transition.To reduce the Doppler broadening effect,Doppler-free two-photon spectroscopy has been used for accurate measurements.This technique,together with selected laser frequencies,can determine the excited state energy and hyperfine splitting intervals of alkali metal atoms at room temperature.In this paper,the measurement of the cesium 7D_5/2excited state's hyperfine splitting intervals and hyperfine interaction constants was experimentally investigated using a ladder-type(852 nm+698 nm)three-level Cs system(6S_1/2?6P_3/2?7D_5/2)with a 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 were demonstrated via transmission enhancement of the locked 852 nm probe laser.The EIT-assisted DROP spectra were employed to study the hyperfine splitting intervals for the Cs 7D_5/2excited state with a room-temperature cesium atomic vapor cell,and the radio-frequency modulation sideband of a waveguide-type electro-optic phase modulator(EOPM)was 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 significantly improve the spectroscopic resolution.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 the Cs 7D_5/2state(HFS_6"-5"=-10.60(17)MHz and HFS_5"-4"=-8.54(15)MHz)were measured and,therefore,the magnetic dipole hyperfine interaction constant(A=-1.70(03)MHz)and the electrical quadrupole hyperfine interaction constant(B=-0.77(58)MHz)were derived for the Cs7D_5/2state.The experimental error mainly resulted from the spectral resolution limitation caused by the wide linewidth of the obtained spectrum and the uncertainty and instability of the function generator,which driving the electro-optical phase modulator.Considering the error of the system,the frequency locking accuracy of the 852 nm laser needs to be improved.The nonlinear frequency scanning of the 698 nm coupling laser also affected the measurement of experimental results.The spectral signal asymmetry also affected the center frequency determined by fitting and resulted in fluctuation of the measurement results.The phenomena of the fluctuation of atomic number density caused by the temperature fluctuation of cesium atom vapor due to the absence of temperature control and non-overlapping beams,thereby affecting the accuracy of hyperfine splitting intervals,need to be further improved.Although a high permeability permalloy metal magnetic shielding device was used to minimize the stray magnetic field,the Zeeman shift also influenced the results.The AC-stack shift causes a measurement error which is related to the laser intensity.These uncertainties all contribute to the errors of the obtained hyperfine spectrum.These constants have important reference value for the improvement of precise measurement and determination of basic physical constants.In this paper,EIT-assisted DROP spectrum is used to measure the hyperfine splitting intervals and hyperfine interaction constants of 7D_5/2states(F"=6),(F"=5)and(F"=4)of ¹³³Cs atom.The main contents are briefly summarized as follows:(1)The related information of spectrum and research status has been introduced,and clarifies the motivation and significance of the research;(2)The theoretical model of the interaction between light and atoms in a two-level system and the EIT model of a three-stepped level system are studied,and the absorption and dispersion characteristics are calculated and analyzed.The relationship between hyperfine splitting and hyperfine interaction constants is introduced.(3)Based on the narrow splitting intervals of cesium atom of 7D_5/2state,the spectral resolution and SNR are further improved through the selection of spectral scheme and the optimization of experimental parameters.A cascade three-level EIT system was constructed,and the EIT-assisted DROP spectra of the 7D_5/2excited state of Cs atom are obtained.(4)The EIT-assisted DROP spectra are employed to study the hyperfine splitting intervals for the Cs 7D_5/2excited state with a room-temperature cesium atomic vapor cell,and the radio-frequency modulation sideband of a waveguide-type electro-optic phase modulator is introduced for frequency calibration to improve the accuracy of frequency interval measurement.Features of this article:1)Using Doppler-free EIT-assisted DROP spectrum;2)The hyperfine splitting of the 7D_5/2state of the Cs atom is measured by scanning the 698 nm laser frequency and applying RF modulation at 698nm.