Novel Method for the Derivation of 1-Phonon Function from Fluorescence Line Narrowing Spectrum

Abstract

Theoretical formulation for fluorescence line narrowing (FLN) spectrum is reinvestigated by using the dynamical theory of electron-phonon interaction. We have found that the formulation becomes very simple in the case of sufficiently large inhomogeneous broadening. With the use of this formulation, 1-phonon function which is defined as a product of linear electron-phonon coupling constant and the density of states of phonon, can be obtained directly from Fourier transform of experimentally observed FLN spectrum. To demonstrate the feasibility of our method, we derive 1-phonon function from the observed FLN spectrum in a sample of tetracene doped in polyisobutylene. By using thus obtained 1-phonon function, the temperature dependence of FLN spectrum can be numerically reproduced without any adjustable parameters. We further consider the influence of inhomogeneous width on the present method for the derivation of 1-phonon function.