目的：量測銫原子6S-7S雙光子之躍遷頻率，以得知精確之7S能階。學術影響：1.提供理論原子物理學家新的實驗數據，使得對銫原子7S超精細能階的波函數，更精準的計算，有利於對弱交互作用中，中性流對宇稱不守恆的影響細節有更多認識。2. 1080-nm穩頻半導體雷射，在知道其絕對頻率後，可成為在1080 nm之二級光鐘。3. 量測這個躍遷的光強頻移，可以校正日本重力波干涉儀中，光子校正法之雷射光強度。 ;Cesium 7S-level is a “landmark-like” atomic level for all the experiments of atomic parity non-conservation (APNC), since it is the only one big stable atom of which the APNC could be calculated with high precision. This is due to the fact that cesium has only one valance electron outside the close shell and, furthermore, the hydrogen-like symmetric S orbit is easier for choosing suitable bases in B-splines in terms of composing an accurate wavefunction in the many-body perturbation theory (MBPT) Moreover, based on our prvious experiment which was once chosen as “Spotlight on Optics 2013” by Optical Society of America (performed totally in our laboratory), the measured absolute transition frequency could also be a good optical secondary clock at 1080 nm due to the good nature of cesium S state that is insensitive to the earth magnetic field. We further propose the application of the related two-photon transition to the photon calibrator project in the GW (gravitational wave) observatories, by using the "linear light shift" feature of the cesium 6S-7S two-photon transition of which the 1080-nm wavelength is perfectly suitable for the mirror coating of the interfrometers used in Japan and United States.