本實驗主要是應用雷射冷凝技術來建造銫原子磁光阱，並且在銫冷原子團中的|9d 2D3/2>、|9d 2D5/2>、|11s 2S1/2>、|10d 2D3/2>、|10d 2D5/2>等原子能階做精密量測。

　　在10-9Torr的超高真空腔中，以磁光阱聚集冷原子團，其填充時間約是6 秒，在直徑2～5mm的原子團中，原子數可達107個，溫度約為100μK。我們將染料雷射引入冷原子團樣本，量測磁光阱中銫原子的螢光減少量，可以得到|9d 2D3/2>、|9d 2D5/2>、|11s 2S1/2>、|10d 2D3/2>、|10d 2D5/2>等原子能階位置。利用準確度小於3MHz，標準差約1.62MHz的碘分子超精細飽和吸收光譜做為頻率的標準尺，並在超低溫的冷原子團中，消除大部分的都卜勒效應，並縮小碰撞增加的譜線變寬與位移，這些能階的絕對能量準確度可達10MHz。在量測銫原子能階位置的過程中，實驗數據出現兩頻峰相距約20~30MHz的分裂，目前我們初步認定這應是電磁波引發透明效應。

　　銫原子的標準量測可以幫助我們瞭解銫原子能階分怖情形，包括提高銫原子鐘的準確度，利用原子干涉量測重力加速度…等。

　We used laser cooling technique to build a magneto-optical trap for cesium atoms. Precision measurement had been performed to determine the atomic energy levels of |9d 2D3/2>, |9d 2D5/2>, |11s 2S1/2>, |10d 2D3/2>, |10d
2D5/2> for the cold cesium atoms.

　Cesium atoms were loaded into the trap from a background vapor cell within a pressure of 10-9 Torr. The loading time was about 6 sec and about 107 cesium atoms were confined inside a sphere of 2~5 mm in diameter and the
temperature of cold atoms was about 100μK.

　　The dye laser overlapped with the atom cloud to excite the cold cesium atoms to |9d 2D3/2>, |9d 2D5/2>, |11s 2S1/2>, |10d 2D3/2>, |10d 2D5/2> states. The signal was monitored by detecting the trap loss while changing the dye laser frequency. The line positions were measured by comparing observed spectrum with molecular iodine saturation absorption spectrum (accuracy <3MHz, std.~1.65MHz) to an accuracy of 10MHz. Doublet peaks splitting of 20 to 30 MHz appear on all lines which could be caused by the electromagnetic induced transparence.

　Precision measure plays an important role in many experiments on atom clock and atom interferometry.

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