Photophysics of Methyl-Substituted Uracils and Thymines and Their Water Complexes in the Gas Phase

摘要: We report studies on several methylated uracils and thymines thymine−water complexes in the gas phase using resonantly enhanced multiphoton ionization (REMPI) laser-induced fluorescence (LIF) spectroscopy. Results from two different REMPI experiments provided strong evidence that, after photoexcitation to S1 state, bare molecules were funneled into trapped a dark state via fast internal conversion. Lifetimes of this determined be tens hundreds nanoseconds, depending energy degree methyl substitution. The mass spectra hydrated thymine clusters demonstrated dependence excitation wavelength, gradual loss ion signal with increasing water content across absorption region indicated reduced lifetime by solvent. In addition, also decreased gradually as became more hydrated. On basis these results, we conclude so...