臺灣博碩士論文加值系統

論 文 摘 要 ：
本篇論文乃研究利用飛行時間質譜儀探討乙烯酮（ketene）離子形成的機制。一般而言光游離（photon-ionization）質譜訊號形成的機制主要有三種：一、先解離再游離（dissociation prior to ionization），即分子吸收光子後先發生解離現象，解離之中性碎片再吸收足夠的光子數目形成碎片離子。二、游離之後再解離（ionization prior to dissociation），分子吸收足夠的光子數目形成離子後，經由解離反應的機制形成碎片離子。三、先形成超激發態(forming super-excited states)再游離，中性的超激發態之能階已經超過第一游離能，分子到達此態之後，進行自動游離的現象。
我們經由一系列的實驗，包括觀測雷射強度（power dependence）、電場強度、延遲電場作用時間、變換乙烯酮濃度，探討乙烯酮游離的途徑。由實驗的結果得知：當乙烯酮分子吸收兩個光子（355 nm）到達雷得堡態，若再吸收一個光子即可游離，即（2+1）游離的方式，其特性與(2+2)游離方式差異很大，前者為直接離化的現象而後者則需先經過超激發態再自動游離生成乙烯酮離子。

The interrelation between and fragmentation of ketene is studied. A jet-cooled ketene is first excited to a 3p Rydberg state prior to ionization with the same laser irradiation; the resultant parent and fragment ions are then detected by a time-of-flight (TOF) mass spectrometer. From the dependence measurement of laser power, ketene pressure, and intensity and duration of a pulsed electric field, we find that the ketene ions are obtained predominantly by an autoionization process from superexcited state. The CH2 ion is fragmented by a dissociative ionization of the superexcited state in competition with the autoionization. The factors of pulse filed and collision may enhance the autoionization rate significantly, leading to an opposite effect on the branching ratio of ketene ion and CH2 ion fragment. In the time-of-resolved ketene ion measurement , we may differentiate two types of ion sourse.

目錄
論文摘要
圖目錄
第一章 緒論 1
1-1 研究動機…………………………………1
1-2 多光子共振游離技術……………………7
1-3 超激發態分子特性………………………14
1-4 電場誘導碰撞增強自動游離原理……17
第二章 飛行時間質譜儀介紹 19
2-1 質量偵測原理……………………………19
2-2 影響解析度的因素……………………24
2-3 兩段式推出電場設計……………………29
2-4 時間延遲聚焦技術………………………34
2-5 離子反射器………………………………36
第三章 實驗操作 40
3-1 藥品備製…………………………………40
3-2 儀器裝置…………………………………42
3-3 實驗程序…………………………………44
第四章 結果與討論 50
4-1 ketene光解與光強度之關係……………51
4-2 超激發態的形成與分解游離機制………57
4-3 電場作用時間與離子訊號之關係………60
4-4 脈衝電場強度與離子訊號之關係………67
4-5 乙烯酮樣品濃度與離子訊號的關係……75
4-6 利用延遲脈衝電場觀測ketene離子訊
號衰減的現象………………………………83
4-7 結論與未來展望 …………………………89
參考文獻 93

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