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研究生: 呂佳佳
Jia- Jia Lyu
論文名稱: 高振動激發態薁分子與單原子氣體─氪氣碰撞能量轉移研究
Energy Transfer of Highly Vibrationally Excited Azulene─Collision between Azulene and Kr
指導教授: 倪其焜
Ni, Chi-Kung
學位類別: 碩士
Master
系所名稱: 化學系
Department of Chemistry
論文出版年: 2006
畢業學年度: 94
語文別: 中文
論文頁數: 64
中文關鍵詞: 交叉分子束能量轉移超級碰撞薁分子
英文關鍵詞: Energy transfer, Azulene, Velocity mapping, supercollision
論文種類: 學術論文
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  • 本研究主要透過交叉分子束及時間切片速度相配離子影像〈time-slice velocity map ion images〉偵測技術,探討高振動激發態薁分子〈Azulene〉與惰性氣體原子─氪〈Kr〉間能量轉移的動態學。其中,高能薁分子是以266 nm〈4.66 eV〉雷射將其激發至S4的電子態,再經快速內轉換〈Internal conversion〉機制所產生的基態電子態上高振動能階之熱分子〈 ‡〉。由於薁分子本身之獨特光物理特性,我們得以利用其產生一高純度的熱分子束,並簡單藉由157 nm及118 nm兩真空紫外光加以定量。從偵測之熱薁分子散射影像,我們便能直接獲得分子碰撞後動能及角度的分佈訊息,並量得特定初始碰撞能量下〈170 cm-1、465 cm-1及780 cm-1〉能量轉移機率分佈函數─ 的全貌。當碰撞能量足夠低時,影像上明顯存在形成Az-Kr的凡得瓦分子,這些凡得瓦分子造成小部分平移動能轉移至薁分子的轉動或振動能階上〈T  V/R的能量轉移〉。此外,實驗上也發現T  V/R的能量轉移效益相當高,某些情況下,分子間的相對動能幾乎完全被轉換成分子的轉動或振動能量。另ㄧ方面,薁分子的振動能量僅小部分比例會轉成平移動能的形式,且此V  T的能量轉移機率分佈曲線需以複合指數函數〈multiexponential function〉描述,薁分子向後散射方向影像並存在高能量轉移的分佈成分,來自於超級碰撞〈supercollision〉的結果。實驗上,碰撞能量465 cm-1及780 cm-1時,薁分子散射方向 所觀測之轉移量 的碰撞成分約為1%及0.3%。

    The energy transfer dynamics between highly vibrationally excited azulene was studied using a crossed-beam apparatus along with time-sliced velocity map ion imaging technique. "Hot" azulene (4.66 eV internal energy) mole- cules and Kr atoms in a series of collision energies (170, 465 and 780 cm-1) was formed via the rapid internal conversion (IC) of azulene initially excited to the S4 state by 266 nm photons. Attributing to the unique photophysical properties,we can create a near pure highly vibrationally excited molecular beam and characterize the relative concentration of hot molecules. The shapes of the collisional energy-transfer probability distribution functions were measured directly from the scattering results of highly vibrationally excited or "hot" azulene. At low enough collision energies an azulene-Kr complex was observed, resulting from small amounts of translational to vibrational/rotational (T-V/R) energy transfer. T-V/R energy transfer was found to be quite efficient. In some instances, nearly all of the translational energy is transferred to vibrational/rotational energy. On the other hand, only a small fraction of vibrational energy is converted to translational energy (V-T). The V-T energy transfer distribution functions were best fit by multiexponential functions. We find that substantial amounts of energy are transferred in the backward scattering direction due to supercollisions at high collision energies. The probability for supercollisions, defined arbitrary as the scattered azulene in the region 160o<<180o and Edown>2000 cm-1, is about 1% and 0.3% of all other collisions at collision energies 465 and 780 cm-1, respectively.

    第一章 緒論----------------------------------------------- 1 1.1 碰撞能量轉移研究的重要性---------------------------------1 1.1.1 碰撞能量轉移機制所扮演的角色--------------------------1 1.1.2 超級碰撞〈Supercollision〉存在的影響-----------------3 1.2 相關實驗研究的突破與限制---------------------------------3 1.2.1 相關實驗技術概述-------------------------------------4 1.2.2 相關研究所面臨的問題---------------------------------5 1.3 交叉分子束實驗研究的契機---------------------------------5 參考文獻-----------------------------------------------7 第二章 實驗設計與可行性評估-----------------------------------8 2.1 儀器裝置與設計-----------------------------------------8 2.1.1 交叉分子束源〈crossed molecular beam〉---------------8 2.1.2 壓差真空腔體〈differentially-pumped vacuum chamber〉 與主腔體-------------------------------------------11 2.1.3 紫外光雷射與真空紫外光雷射---------------------------11 2.1.4 離子偵測設備---------------------------------------13 2.1.5 實驗設計原理---------------------------------------14 2.2 實驗設計的沿革與可行性評估------------------------------16 2.2.1 單分子束碰撞的評估----------------------------------16 2.2.2 非預期中的困境─團簇〈clusters〉存在的影響------------19 2.2.3 交叉分子束碰撞的評估--------------------------------20 2.3 能量校準與影像解析度測量--------------------------------23 參考文獻----------------------------------------------26 第三章 高振動激發態分子的產生--------------------------------27 3.1 薁分子的光物理特性-------------------------------------27 3.2 高純度熱分子束的產生-----------------------------------29 3.2.1 定量分子束中高振動激發態分子存在的比例----------------30 參考文獻----------------------------------------------33 第四章 實驗結果與分析方法------------------------------------34 4.1 高振動激發態薁分子與單原子惰性氣體的碰撞能量轉移-----------34 4.1.1 實驗所得影像的初步分析------------------------------34 4.1.2 影像靈敏度校準(sensitivity calibration)------------38 4.1.3 不同形式的碰撞能量轉移------------------------------46 4.1.4 真實散射熱薁分子影像分佈----------------------------48 4.1.5 能量轉移機率分佈函數--------------------------------48 4.1.6 形成凡得瓦分子的碰撞--------------------------------57 4.1.7 超級碰撞〈Supercollision〉的證據--------------------58 4.1.8 全碰撞與半碰撞-------------------------------------60 參考文獻-------------------------------------------62 第五章 結語與展望-------------------------------------------63 圖目錄 圖2.1 實驗儀器側視圖--------------------------------------------------------- 9 圖2.2 實驗儀器俯視圖--------------------------------------------------------- 10 圖2.3 交叉分子束與激發及游離雷射的相對位置示意圖--------------- 12 圖2.4 聚焦離子板的裝設與電壓配置圖------------------------------------ 13 圖2.5 快速離子偵測器所測得波形的半高寬及時間--------------------- 17 單分子束碰撞簡圖------------------------------------------------------ 17 圖2.6 交叉分子束碰撞簡圖--------------------------------------------------- 20 圖2.7 系統之能量校準實驗裝置架設、相關位能曲線及偵測影像圖 24 圖3.1 薁分子〈Azulene〉結構及游離能量----------------------------------- 27 圖3.2 薁分子電子態能階圖--------------------------------------------------- 28 圖3.3 薁分子離子訊號〈Azulene+─m/e=128〉隨激發雷射強度變化 之分佈圖------------------------------------------------------------------ 32 圖4.1 碰撞能量為170 cm-1時的影像及牛頓球圖------------------------- 35 圖4.2 碰撞能量為465 cm-1時的影像及牛頓球圖------------------------- 36 圖4.3 碰撞能量為780 cm-1時的影像及牛頓球圖------------------------- 37 圖4.4 碰撞散射球因碰撞時間點飛散及擴大之關係圖------------------ 39 圖4.5 薁分子束、氪氣氣體分子束、266 nm激發雷射及157 nm游 離雷射在空間中之相對位置圖--------------------------------------- 40 圖4.6 薁分子速度、氪氣氣體原子速度、質心速度及相關速度向量 分佈圖--------------------------------------------------------------------- 41 圖4.7 薁分子束脈衝中之各成分相對比例分佈關係圖------------------ 44 圖4.8 碰撞能量465 cm-1時,以速度〈實驗室坐標〉函數表示的靈 敏度校準矩陣------------------------------------------------------------ 45 圖4.9 相關文獻對於相同碰撞系統,應用不同研究技術所得平均能 量訊息的比較圖--------------------------------------------------------- 50 圖4.10 VT能量轉移機率分佈函數圖-------------------------------------- 51 圖4.11 TV/R能量轉移機率分佈函數圖----------------------------------- 52 圖4.12 VT能量轉移總機率分佈函數圖----------------------------------- 55 圖4.13 TV/R能量轉移總機率分佈函數圖-------------------------------- 56 圖4.14 形成凡得瓦分子的碰撞機制概念圖--------------------------------- 58 圖4.15 Oref等人對於超級碰撞〈supercollision〉機制的兩種解釋圖----- 59

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