Photophysics of 2- and 3-fluoropyridine vapors

Emission and excitation spectra of 2- and 3-fluoropyridine (2- and 3-FP, respectively) vapors have been measured under the different conditions. It is shown that 3-FP vapor emits weak fluorescence from the S1(n, π∗) states. The fluorescence quantum yields are evaluated to be approximately 10−3 and 10−4 for 2- and 3-FP vapors, respectively, following the excitation into the S1 origin. The fluorescence yields decrease significantly with increasing excitation energy. The decrease of the yield is more significant for 2-FP than for 3-FP vapor. The data include vibrational analyses of the hot bands in the excitation spectra using the DFT calculation at the B3LYP/6-311++G∗∗ level.