旋轉異構物3,4-二氟苯酚及2,5-二氟苯酚之質量解析臨界游離光譜研究

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2014

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本實驗使用單色共振雙光子游離光譜術、雙色共振雙光子游離光譜術以及質量解析臨界游離光譜術來探討3,4-二氟苯酚以及2,5-二氟苯酚的分子特性,並且利用上述的光譜術去獲得此分子的第一電子激發態能量、游離能以及經由第一電子激發態和離子態的振動光譜。因為3,4-二氟苯酚以及2,5-二氟苯酚這兩個分子皆具有兩種不同的旋轉異構物,分別為順式3,4-二氟苯酚和反式3,4-二氟苯酚以及順式2,5-二氟苯酚和反式2,5-二氟苯酚。順式3,4-二氟苯酚和反式3,4-二氟苯酚所獲得的躍遷能和游離能分別是35 486 ± 2和35 704 ± 2 cm-1以及70 016 ± 5 和70 203 ± 5 cm-1;而順式2,5-二氟苯酚和反式2,5-二氟苯酚的躍遷能和游離能分別為36 448 ± 2和36 743 ± 2 cm-1以及71 164 ± 5和71 476 ± 5 cm-1。我們可以觀察到在反式結構中,其躍遷能和游離能都略高於順式的結構。經由光譜分析所獲得的結果顯示出造成此結果的原因為平面運動苯環的變形和取代基彼此互相作用有關。綜合三種光譜術所獲得的光譜分析,可得到一個結論,在順式和反式的旋轉異構物中,不管是利用在電子激發的中性物種或是在陽離子基態,其分子的幾何形狀和振動座標都是相似的。
We applied the resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic and cation spectra of 3,4-difluorophenol (34DFP) and 2,5-difluorophenol (25DFP). The band origins of the S1 ← S0 electronic transition of the cis and trans rotamers of 34DFP are found to be 35 486 ± 2 and 35 704 ± 2 cm-1 and the adiabatic ionization energies are 70 016 ± 5 and 70 203 ± 5 cm-1, respectively. The excitation energy of the S1 ← S0 electronic transition of the cis and trans rotamers of 25DFP are found to be 36 448 ± 2 and 36 743 ± 2 cm-1 and the adiabatic ionization energies are 71 164 ± 5 and 71 476 ± 5 cm-1, respectively. The distinct spectral features mainly result from the in-plane ring deformation and substituent-sensitive bending vibrations. Spectral analysis suggests that the molecular geometry and vibrational coordinates of the cation in the D0 state resemble those of the neutral species in the S1 state for both cis and trans rotamers.

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3, 4-二氟苯酚, 2, 5-二氟苯酚, 質量解析臨界游離光譜, 3, 4-difluorophenol, 2, 5-difluorophenol, MATI spectrum

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