| Abstract
| - Fluorescence excitation, multiphoton ionization, and dispersed fluorescence spectra of bare and hydrogen-bonded 2-fluoropyridine with water were measured in a supersonic free jet. For bare 2-fluoropyridine,fluorescence quantum yield decrease in the higher vibronic levels was observed even under collision-freeconditions. The intersystem crossing channel was probed experimentally by two color R2PI and found to benegligible. The nonradiative relaxation process of 2-fluoropyridine is mainly governed by the relaxation tothe electronic ground state. Electronic spectra of 2-fluoropyridine−(water)n (n = 1∼3) were also obtained.The hydrogen bond formation with water increases the quantum yield in the higher vibronic levels. Ratherlow frequency vibrations were observed in the hole burning spectrum of bare 2-fluoropyridine; however,these vibronic bands disappeared with the hydrogen bond formation with water. The appearance of lowfrequency vibronic bands observed for bare 2-fluoropyridine is ascribed to the existence of closely lying(n,π*) state.
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