三取代基苯衍生物3,5-二氟苯酚之第一電子激態暨離子態振動光譜
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2016
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本論文研究著重於探討3,5二氟苯酚的特性，所使用的實驗技術包括單色共振雙光子游離(1C-R2PI)光譜術、雙色共振雙光子游離(2C-R2PI)光譜術和質量臨界游離(MATI)光譜術，利用以上技術可得知分子的第一電子激發能量、絕熱游離能和電子激發態與離子態分子振動光譜。本次的實驗，我們使用單光共振雙光子游離術精準地測量出3,5二氟苯酚的第一激發態能量為 37 614 ± 2 cm-1 且第一激發態的分子振動光譜訊雜比非常良好，可以很明顯地分辨出是否為真實訊號及雜訊。擁有完整的第一激發態資訊後我們利用質量臨界游離光譜術以S100、S110b1、S19b1為中間態得到準確的絕熱游離能 72 468 ± 5 cm-1 以及離子態分子振動光譜。而在數據分析上，我們參考Varsanyi所著的Assignments for Vibrational Spectra of Seven Hundred Benzene Derivatives書中所列的實驗數據再搭配理論計算所得的結果做譜線標定。相較於實驗室之前所測量的二氟苯酚的位置同分異構物， 3,5-二氟苯酚的第一激發能與游離能都為最高。除了電子躍遷能和電子激發態與離子態分子振動的討論之外，我們也會利用量子化學計算探討3,5-二氟苯酚在基態(S0)、第一激發態(S1)與游離態(D0)時的結構變化，發現在電子躍遷時苯環的結構發生改變，此結果與實驗所見到的現象符合。
The thesis focuses on investigateing the cationic properties of 3,5-difluorophenol in the D0 state by several intermediate vibrational levels in S1 state. Our laboratory utilizes resonant two-photon ionization (R2PI), mass-analyzed threshold ionization (MATI) to get the vibrational spectra that can also determine the excitation energy (E1) and adiabatic ionization energy (IE). In this project, I use the 1C-R2PI technique to obtain the vibronic spectrum that provides the accurate first electronic excitation energy and some vibrational modes in first electronically excited (S1) state. In the vibronic (1C-R2PI) spectrum the band origin of S1←S0 transition appears at 37 614 cm-1. The signal/noise ratio is so excellent that we can easily to distinguish vibronic bands of molecular vibrations 10b, 15, 9b, 14. The ionic spectrum recorded by MATI technique. The cationic ground (D0) state of 3,5-difluorophenol is 72 468 ± 5 cm-1. In MATI spectra, the molecule is different from other case. We use the 10b and 9b levels in the S1 to be intermediate states to record the cation spectra. However, spectral features corresponding to the 10b and 9b cation vibrations do not appear in the MATI spectra. This indicates that the transition does not follow the Franck-Condon principle. Our theoretical calculations show that the geometry of 3,5-difluorophenol is changed upon D0←S1 transition. Therefore, the calculated results support our experimental findings.
The thesis focuses on investigateing the cationic properties of 3,5-difluorophenol in the D0 state by several intermediate vibrational levels in S1 state. Our laboratory utilizes resonant two-photon ionization (R2PI), mass-analyzed threshold ionization (MATI) to get the vibrational spectra that can also determine the excitation energy (E1) and adiabatic ionization energy (IE). In this project, I use the 1C-R2PI technique to obtain the vibronic spectrum that provides the accurate first electronic excitation energy and some vibrational modes in first electronically excited (S1) state. In the vibronic (1C-R2PI) spectrum the band origin of S1←S0 transition appears at 37 614 cm-1. The signal/noise ratio is so excellent that we can easily to distinguish vibronic bands of molecular vibrations 10b, 15, 9b, 14. The ionic spectrum recorded by MATI technique. The cationic ground (D0) state of 3,5-difluorophenol is 72 468 ± 5 cm-1. In MATI spectra, the molecule is different from other case. We use the 10b and 9b levels in the S1 to be intermediate states to record the cation spectra. However, spectral features corresponding to the 10b and 9b cation vibrations do not appear in the MATI spectra. This indicates that the transition does not follow the Franck-Condon principle. Our theoretical calculations show that the geometry of 3,5-difluorophenol is changed upon D0←S1 transition. Therefore, the calculated results support our experimental findings.
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3, 5-二氟苯酚, 質量解析臨界游離光譜術, 共振游離雙光子游離光譜術, 3, 5-Difluorophenol, Mass analyzed threshold ionization, Resonance-enhanced multiphoton ionization