## 6 [PERSON] and Outlook  
In conclusion, we measured the hyperfine splitting intervals and derived the hyperfine interaction constants of the Cs 5\(p^{6}\)7\(d\)\({}^{2}D_{5/2}\) excited state. Cs atoms were excited from the ground state 5\(p^{6}\)6s \({}^{2}S_{1/2}\) to the excited state 5\(p^{6}\)7\(d\)\({}^{2}D_{5/2}\) (\(F^{\prime\prime}\) = 6, 5, 4) through the ladder-type 5\(p^{6}\)6s \({}^{2}S_{1/2}\)-5\(p^{6}\)6\(p\)\({}^{2}P_{3/2}\)-5\(p^{6}\)7\(d\)\({}^{2}D_{5/2}\) three-level system. The EIT-assisted DROP and OODR spectroscopic schemes were compared, and EIT was employed to obtain improved SNR and higher resolution. The effects of the 852 nm probe beam's linewidth and of the optical intensity of the 852 nm probe beam and 698 nm coupling beam on the spectroscopic amplitude were investigated. After choice of the spectroscopic scheme and optimization of the experimental parameters, the Cs 5\(p^{6}\)7\(d\)\({}^{2}D_{5/2}\) state's hyperfine splitting intervals between (\(F^{\prime\prime}\) = 6), (\(F^{\prime\prime}\) = 5), and (\(F^{\prime\prime}\) = 4) hyperfine folds were measured (HFS\({}_{6^{\prime\prime}\text{-}5^{\prime\prime}}\) = \(-\)10.60(17) MHz and HFS\({}_{5^{\prime\prime}\text{-}4^{\prime}}\) = \(-\)8.54(15) MHz) by introducing EOPM to provide modulation sidebands for frequency calibration. Furthermore, the hyperfine interaction constants (\(\mathbf{A}\) = \(-\)1.70(03) MHz, the magnetic dipole constant; \(\mathbf{B}\) = \(-\)0.77(58) MHz, the electrical quadrupole constant) were derived for the Cs 5\(p^{6}\)7\(d\)\({}^{2}D_{5/2}\) state. The measurement results were found to be consistent with previous measurement results, thereby providing an improved foundation for further relevant theoretical and experimental studies.  
The combination of atomic coherence and optical pumping spectroscopy allowed the EIT-assisted DROP spectroscopic scheme to achieve improved SNR and a higher frequency resolution, which is of great significance for the precise measurement. On the other hand, it provides an important reference value for measuring the internal structure of atoms to deal with PNC and other related studies.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \(\mathbf{A}\) (MHz) & \(\mathbf{B}\) (MHz) & **Reference/Year** \\ \hline \(-\)1.70 (03) & \(-\)0.77 (58) & This work \\ \(-\)1.79 (05) & \(+\)1.05 (29) & [29] (2020) \\ \(-\)1.81 (05) & \(+\)1.01 (1.06) & [27] (2011) \\ \(-\)1.717 (015) & \(-\)0.18(52) & [28] (2010) \\ \(-\)1.56 (09) & - & [34] (2007) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Magnetic dipole (\(\mathbf{A}\)) and the electrical quadrupole (\(\mathbf{B}\)) hyperfine interaction constants of the Cs 5\(p^{6}\)7\(d\)\({}^{2}D_{5/2}\) state.  
**Author Contributions:** [PERSON] proposed and supervised the project. [PERSON] and [PERSON] set up the ladder-type EIT system. [PERSON] measured and collected the experimental data. [PERSON] and [PERSON] fitted the experimental data. [PERSON] and [PERSON] analyzed all the experimental data, then wrote and revised the manuscript. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research is partially supported by The National Key R&D Program of China, [grant number 2017 YFA0304502], the National Natural Science Foundation of China, [grant numbers 11774210, 11974226, 61875111, and 61905133], and the Shanxi Provincial 1331 Projects for Key Subjects Construction.  
**Conflicts of Interest:** The authors declare no conflict of interest.