臺灣博碩士論文加值系統

The excited-state dynamics of o-hydroxyacetophenone (OHAP) and its related molecules have been studied in the gas phase using femtosecond time-resolved multiphoton ionization spectroscopy. Following femtosecond excitation to their S1 state, the OHAPs were found to exhibit a biexponential decay behavior coupled with a rapidly damped low-frequency oscillation. The hydroxy deuterated OHAP showed a significant isotope effect, indicating that the oscillation is related to the H-atom motion. The combination of experimental and theoretical results suggested that, although the initial motion in the excited-state intramolecular proton transfer occurs in less than 100 fs, a low-frequency vibration motion involving both O…O and O-H stretches may allow the system to oscillation between the two tautomeric forms.

Abstract ……………………………………………………………………i
Acknowledgements …………………………………………………………ii
Contents ……………………………………………………………………iii
List of figures……………………………………………………………v
List of tables ……………………………………………………………ix
Chapter 1: Introduction …………………………………………………1
1.1 Excited state intramolecular proton transfer (ESIPT) …2
1.2 A brief review on o-hydroxybenzaldehyde (OHBA) …………4
1.3 A brief review on o-hydroxyacetophenone (OHAP) …………9
1.4 This work …………………………………………………………12
Chapter 2: Experimental…………………………………………………30
2.1 Methodology ………………………………………………………30
2.2 Experimental setup………………………………………………33
2.2.1 Ultrafast laser system ………………………………33
2.2.2 Optics layout……………………………………………36
2.2.3 Flow cell…………………………………………………38
2.2.4 Molecular beam apparatus ……………………………40
2.2.5 Time-of-flight mass spectrometer (TOF-MS)………43
2.2.6 Data acquisition ………………………………………45
2.3 Cross correlation ………………………………………………47
2.4 Chemicals …………………………………………………………48
2.5 UV absorption spectra …………………………………………50
Chapter 3: Experimental Results and Analyses ……………………67
3.1 OHAP transients and data analyses …………………………67
3.2 Laser irradiance dependence …………………………………70
3.3 Pump-laser wavelength dependence of the transients……72
3.4 Substitution position effect: OHAP and MHAP ……………74
3.5 Alkyl-substitution position effect: OHAP and MHAP ……75
3.6 Isotope effect: OHAP and ODAP ………………………………77
Chapter 4: Theoretical Calculation and Discussion………………94
4.1 Reaction mechanism………………………………………………94
4.2 Ab initio calculations…………………………………………96
4.2.1 Vertical excitation and ionization energy………96
4.2.2 Potential energy profile along the S1(p,p*) CIS-
MEP…………………………………………………………99
4.2.3 Potential energy surface of S1(p,p*) state……102
4.3 Low-frequency vibrational motion …………………………103
4.4 The origin of transient oscillation………………………104
4.5 Dynamic of proton transfer reaction………………………105
Chapter 5: Conclusion …………………………………………………118
Chapter 6: Reference……………………………………………………120

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