Electric field effects on absorption and fluorescence spectra of pyrene doped in a PMMA polymer film

Abstract

Electric field modulated absorption, fluorescence and fluorescence excitation spectra of pyrene doped in a PMMA polymer film were measured with excitation from 220 to 380 nm. The observed spectra of the field-induced change in absorption intensity or fluorescence intensity for each electronic transition agree well with the first derivatives of the corresponding absorption or fluorescence spectrum, indicating that the field effect results from the Stark shift induced by a change in molecular polarizability between the ground state and the excited state. The magnitude of the change in polarizability was evaluated for the first, S 1( 1L b), the second, S 2( 1B a), the third, S 3( 1B b), and the fourth, S 4( 1L a), optically spin-allowed absorption bands. The change in average polarizability following excitation is found to be in the order of S 1<S 4<S 3<S 2, and all the polarizabilities in the excited states are larger than in the ground state. The third nonlinear order susceptibility ( χ (3)) of a pyrene-doped PMMA film was also calculated on the basis of the electroabsorption and electrofluorescence excitation spectra.