Dispersed fluorescence spectroscopy of 2-hydroxypyridine and its cyclically hydrogen-bonded water clusters in the gas phase: An examination of occurrence of excited-state proton transfer

The fluorescence excitation and dispersed fluorescence spectra of 2-pyridone (2PY), 2-hydroxypyridine (2HP), and 2HP(H2O)n (n = 1, 2) clusters in the electronic excited π–π∗ state have been measured in a supersonic free jet expansion. The photoexcitation of various vibronic bands in the excited state of 2HP(H2O)n (n = 1, 2) does not provide fluorescence from 2PY(H2O)n (n = 1, 2) that can be formed by the excited state intermolecular proton transfer (ESPT), suggesting that ESPT is a minor decay channel from the excited state of 2HP(H2O)n (n = 1, 2).