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研究生： 徐偉珉
Hsu, Wei-Min
論文名稱： 鉈原子 6P1/2 → 6P3/2 之 χ=E2/M1 躍遷振幅比例的量測
Measurement of =E2/M1 amplitude ratio of atomic thallium 6P_1/2 → 6P_3/2
指導教授： 劉怡維
Liu, Yi-­Wen
口試委員: 陳應誠
Chen, Ying-Cheng
王立邦
Wang, Li-Bang
學位類別： 碩士
Master
系所名稱： 理學院 - 物理學系
Department of Physics
論文出版年： 2021
畢業學年度： 109
語文別： 中文
論文頁數： 34
中文關鍵詞： 鉈 、躍遷振幅比例 、電磁引發透明
外文關鍵詞： amplitude ratio, Electromagnetically induced transparency,
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    • 這篇論文中，我們研究了鉈原子 (Thallium) 的電磁誘發透明 (EIT) 效 應和宇稱不守恆 (PNC) 之間的關係，並運用實驗得到的結果計算電四極 (E2) 和磁二極 (M1) 的躍遷振幅的比值 (E2/M1)，利用階梯式電磁引發透 明消除都卜勒增寬，完全解析兩條相互對比的譜線。實驗使用兩個不同 的雷射光源，第一個是量子點二極體 (Quantum­dot diode) 的外腔式半導體 雷射產生 1283nm 的紅外光，第二個是透過 1070nm 倍頻產生的 535nm 綠 光。我們也利用寬頻 EOM 的特性消除光強不穩的主要誤差，經過聲光 調製器 (AOM) 調製的一階 535nm 綠光停在 |6P3/2, F = 1> → |7S1/2, F = 0>， 同時讓經過光纖耦合的電光調製器 (Fiber EOM) 的 1283nm 紅外光產生和 中心頻率相距 10.4GHz 的 sideband，掃過 |6P1/2, F = 0> → |6P3/2, F = 1> 和 |6P1/2, F = 1> → |6P3/2, F = 1> 兩個躍遷。兩道光在約 600°C 的 thallium cell 中重疊得到兩個不同的 EIT 訊號，雷射主頻只需掃動數百 MHz，即可得到 原本相距 21GHz 的光譜訊號。紀錄不同幫浦光與探測光偏振夾角下的訊 號，以取得訊號最大值以及曲線擬合的方式，得出兩條譜線強度的比值， 以計算在宇稱不守恆中與弱交互作用相關的重要參數 χ，也就是躍遷振幅 的比值 (E2/M1)，曲線擬合方法結果為 χ = 0.2516 ± 0.0084，與理論計算結 果 (0.254) 一致，但和先前實驗的數值 0.24 有一個標準差的差異。

    In this thesis, we utilized the electromagnetically induced transparency (EIT) spectroscopy to measure transition amplitude ratio of electric quadrupole (E2) and magnetic dipole (M1) of 6P1/2→6P3/2 of atomic thallium, which plays a crucial role in the measurement of parity non­conservation. EIT was used to eliminate the Doppler broadening to resolve the transitions from overlapping signals of dif­ ferent isotopes. We use two different laser sources in our experiment, the first is 1283nm infrared light generated by quantum­dot (QD) external cavity diode laser, and the second is 535nm green light generated by 1070nm laser frequency dou­ bling. A broad band Electro­optical modulator was used to reduce the major sys­ tematic error of the power instability. The 535nm laser is modulated by AOM to perform the modulation transfer spectroscopy, and its frequency is at the resonance of |6P3/2, F = 1> → |7S1/2, F = 0>. The 1283nm laser is coupled into a fiber­based EOM and generate 10.4GHz sideband, therefore it scans through |6P1/2, F = 0> → |6P3/2, F = 1> and |6P1/2, F = 1> → |6P3/2, F = 1> transitions just by hundreds MHz tuning, because the two sideband are ∼21GHz apart, close to the separation of the transitions to be measured. Two lasers overlap in 600°C thallium cell for EIT spectroscopy. We recorded the signals with various polarization angles to cal­ culate the χ = E2/M1 using the peak heights of signal and the theoretical profile model fitting to find the transition strengths of two transitions. The result, using fit­ ting method is χ = 0.2516 ± 0.0084, which agrees with the theoretical calculation 0.254, but with 1σ away from the previous experimental measurement.

    誌謝 摘要 Abstract ii Contents 1 介紹 1.1 宇稱不守恆(PNC)[1] .............................. 1 1.2 電磁引發透明 (Electromagnetically induced transparency, EIT) . . . . . . . . 2 1.3 Thallium...................................... 4 2 實驗系統 7 2.1 1283nm外腔式半導體雷射源[1]........................ 7 2.2 535nm雷射源 .................................. 10 2.3 Thalliumcell及加熱裝置 ............................ 11 3 實驗 3.1 實驗架設..................................... 16 3.2 系統誤差..................................... 19 3.2.1 半波長板(Half­waveplate) ....................... 19 3.2.2 分色鏡(Dichroicmirror)......................... 20 3.2.3 加熱溫度................................. 21 3.3 訊號測量方式 .................................. 22 4 實驗結果 25 4.1 訊號圖形..................................... 25 4.2 數據分析(最大值、曲線擬合) ......................... 26 5.1 結果討論及未來工作 33 5.1 結果討論..................................... 5.2 未來工作..................................... 33 References 34

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