- 學位論文
低溫鉀分子之光結合光譜
Photoassociation Spectroscopy of Ultracold Potassium molecule
摘要
本實驗主要是研究在低溫鉀原子中的光譜。我們以磁光陷阱的方式產生約107個39K原子，溫度達到0.5-1 mk的低溫39K原子。我們的實驗進行了3種光譜研究：39K的D2譜線的冷原子螢光光譜、D_1 line與光結合光譜的磁光陷阱損耗光譜(trap loss)。冷原子螢光光譜利用調變AOM頻率電壓來得到在D_2 line附近的超精細結構光譜線，並且結果能夠大致對應國際間所測量的結果。陷阱損耗光譜則以單頻可調的Ti-Sapphire雷射，其強度為200 mW，激發低溫鉀原子引發原子逃離，進行光譜研究。我們觀察到D_1譜線的超精細結構光譜，得到超精細結構的譜線且譜線線寬約10 MHz~15 MHz。同時也利用D_1譜線的光譜校準Ti-Sapphire的頻率。光結合光譜，則是將Ti-Sapphire laser頻率調變接近D_2與D1 line附近。在D2附近，我們可以得到約13 %凝聚損耗。在接近D1躍遷附近的光結合光譜則觀察到約6 %凝聚損耗。該結果驗證了以光結合方式產生低溫鉀分子的可行性。未來可以用於研究低溫原子-分子碰撞實驗的研究。
並列摘要
The goal of this experiment is to study the spectroscopy of ultracold potassium atoms. We trapped approximately 〖10〗^7 (_^39)K atoms by magneto-optic trap (MOT) and the temperature of ultracold (_^39)K atoms reached 0.5 mK ~1 mK. Three spectroscopies: the fluorescent spectroscopy of the D_2 line of ultracold (_^39)K potassium atom, the trap loss spectroscopy of the D_1 line, and the trap loss spectroscopy of the molecular photoassociation. The fluorescent spectroscopy of ultracold atoms was performed by changing the frequency of AOM to access the hyperfine spectroscopy of the D_2 line and the result was in a good agreement with the measurements of the previous experiments. The trap loss spectroscopy of the molecular photoassociation was to use a Ti-Sapphire laser with 200 mW output power to excite the ultracold atom pair. The trap losses signal are due to the energy release and the increase of atomic kinetic energy. We observed the hyperfine structure and the linewidth of the spectrum is about 10 MHz to 15 MHz. The D_1 spectroscopy was also used to calibrate the frequency of our Ti-Sapphire laser. The photoassociation spectroscopy was performed in the regions where the excited levels near the D_1 and D_2 transitions. Around the D_2 line, we obtained a trap loss of about 13 %. In the other hand, the photoassociation spectroscopy is observed with 6 % trap loss around D_1 line. The results show that it is possible to form ultracold potassium molecules by photoassociation. It could be used to study the collision of ultracold atoms and ultracold molecules in the future.