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研究生:鄭毓璿
研究生(外文):Yu-Hsuan Cheng
論文名稱:鉀-39之磁費許巴赫共振
論文名稱(外文):Magnetic Feshbach Resonances of Ultracold K-39 Atoms
指導教授:易富國
指導教授(外文):Fu-Goul Yee
口試委員:林育如劉怡維林俊達
口試委員(外文):Yu-Ju LinYi- Wei LiuGuin-Dar Lin
口試日期:2014-07-16
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:物理研究所
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2014
畢業學年度:103
語文別:中文
論文頁數:100
中文關鍵詞:磁費許巴赫共振鉀-39原子次都卜勒冷卻塞曼減速管
外文關鍵詞:magnetic Feshbach resonancespotassium-39sub-Doppler coolingZeeman slower
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本實驗完成全光學式(all-optical configuration) 鉀-39原子之玻色-愛因斯坦凝結(Bose-Einstein condensates) 實驗之前期架設,並且取得該原子於基態|F = 1>各磁量子數之磁費許巴赫共振譜線(magnetic Feshbach resonances)。實驗裝置包含塞曼減速管(Zeeman slower)、磁光阱(magneto-optical trap, MOT)、光阱(optical dipole trap, ODT),本實驗分析並優化實驗條件。配合塞曼減速管,磁光阱的載入速率增加七倍,其載入速率為1.6秒,三秒約有10^8顆原子。經過次都卜勒冷卻(sub-Doppler cooling),於磁光阱之原子的溫度從2 mK降溫至80 K。目前光阱已成功載入10^6顆原子。因為鉀-39 具有吸引的原子交互作用力,不利於進一步之相空間提升,因此採取磁費許巴赫共振以調整原子散射態(scattering state) 與分子束縛態(bound state) 之耦合(coupling),進而改變原子交互作用力。目前磁場可高達近300 G。由於本實驗原子團製備過程為全光學式,其保留了各磁量子數之原子,因此將實驗獲得之共振磁場譜線與理論對照,已取得基態|F = 1>純化之磁量子數――mF = (1; 1) 與mF = (0; 0) 之費許巴赫共振譜線。

This study has completed initial set-up of potassium-39 Bose-Einstein condensates (BEC) and demonstrated the magnetic Feshbach resonances of atoms prepared by all-optical configuration. The experiment starts with loading a magneto-optical trap (MOT) from a Zeeman slower. Subsequently the laser-cooled atoms are then loaded into an optical dipole trap (ODT). With the slower, the loading rate increases by nearly 30 times. The MOT loading time constant achieves 1.6 s and the saturated atom number is equivalent to 10^8 at a temperature of 2 mK. After sub-Doppler cooling, the MOT temperature reaches 80 K and 10^6 atoms are successfully loaded in ODT. Since potassium-39 inherently has attractive interatomic interaction, which is detrimental to phase-space density enhancement of the atoms, Feshbach resonances is implemented to tune the coupling of a scattering state and a bound state of two colliding atoms. With cold atoms, which preserves Zeeman sub-levels states, two scattering channels with pure polarization–mF = (1,1) and mF = (0,0) of the F = 1 manifold have been observed. All information is enclosed in detail
in this thesis.


誌謝iii
摘要v
Abstract vii
1 序論 1
2 實驗原理與技3
2.1 雷射冷卻 3
2.2 塞曼減速管 5
2.3 逆光泵雷射光 6
2.4 磁光阱 6
2.4.1 次都卜勒冷卻 8
2.4.2 玻色鉀原子極窄超精細結構之考慮 8
2.5 光偶極阱 9
2.5.1 光阱之空間分布與振盪頻率. 12
2.6 費許巴赫共振 13
2.6.1 分子位能 13
2.6.2 散射長度 13
2.6.3 磁費許巴赫共振 15
2.6.4 鉀-39 之磁費許巴赫共振 17
3 實驗系統架設 19
3.1 真空腔 19
3.1.1 原子束裝置 21
3.1.2 減速管長度 23
3.1.3 真空系統設計 24
3.1.4 腔體溫度控制 25
3.2 雷射光路架設 25
3.2.1 雷射系統簡介 26
3.2.2 鎖頻系統 27
3.2.3 光路設計 31
3.2.4 另加偏極分光晶體解決保偏單模光纖之些微偏振晃動 34
3.3 磁場線圈 36
3.3.1 多層厚度隨位置改變之塞曼減速管 36
3.3.2 磁光阱/費許巴赫線圈與抵銷線圈 40
3.4 光偶極阱之架設 46
3.5 儀器控制 46
4 原子物理量之探測方法 55
4.1 成像方式 55
4.1.1 吸收影像法 55
4.1.2 螢光影像法 57
4.1.3 成像方式之比較 58
4.2 原子數 58
4.3 原子團溫度 58
4.4 原子團密度峰值 59
4.5 原子束速度 60
5 實驗結果與討論 63
5.1 塞曼減速管之低速原子束 63
5.1.1 慢原子束的速度分布 64
5.2 磁光阱之載入 66
5.2.1 磁光阱與塞曼減速管之實驗架設參數 66
5.2.2 載入速率與碰撞損失係數 67
5.3 光阱之載入 73
5.3.1 次都卜勒冷卻 73
5.3.2 光阱 73
5.4 磁費許巴赫共振實驗 75
5.4.1 所得譜線與理論、他人結果對照 80
6 結論與展望 81
6.1 結論 81
6.2 展望 81
A 鉀原子簡介 83
B 真空系統設計之梯度壓力幫浦機制計算 89
B.0.1 冷卻直通管內之蒸氣壓 89
B.0.2 冷卻直通管出口之孔徑 89
B.0.3 塞曼減速管之孔徑 90
參考文獻 93

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