FLUORESCENCE OF THYMINE IN AQUEOUS SOLUTION AT 300° K

Abstract— –Fluorescence of thymine in neutral aqueous solution at room temperature has been detected using the multiscaling operation of a multichannel analyzer. The emission maximum (2.96 μm^-1) and 0-0 transition energy (3.37-3.45 μm^-1) are close to those determined at liquid nitrogen temperature in mixed solvents. The quantum efficiency of fluorescence excited at 3.77 μm^-1 is calculated to be 1.04 × 10^-4.
The corrected relative excitation spectrum shows significant differences from the absorption spectrum when both are determined under identical conditions of concentration and spectral bandwidth on the same instrument. The quantum yield of fluorescence decreases about 2-fold as the energy of excitation is increased beyond the 0-0' transition and follows the relation 1/φ°α E _excit..
This behavior is discussed in terms of (a) n π* and ππ* states, (b) emission from a minor tautomer and (c) kinetics of competing deactivation processes.