Fluorescence of 5-fluorouracil upon the transition from the second singlet excited state S 2 to the ground state

Abstract

Effect of the wavelength of excitation light (λex) on the fluorescence excitation and emission spectra of 5-fluorouracil in acidic solution (pH 2.5) was studied upon excitation at the S2 ← S0-transition absorption band. It has been found that direct excitation at the second or the shorter wavelength absorption band results in 5-fluorouracil fluorescence that originates not only from the first excited state S1 but is also due the transition from the second excited state S2 to the ground state.