Influence of rotational diffusion on the electric field induced effect on the fluorescence spectrum of diluted solutions I. Theory and numerical simulations Original Research Article

The theory for the calculation of excited state dipole moments from electrooptical emission measurements, developed by Baumann and Deckers (Ber. Bunsenges. Phys. Chem. 81 (1977) 786) presupposes a Boltzmann distribution for the emitting molecules. Using the anisotropic rotational diffusion model and taking into account all important electric field induced effects, we derive equations that describe quantitatively the electric field effect on the fluorescence of an ensemble of solute rigid molecules which are not yet equilibrated with respect to their orientation when emitting. Numerical simulations are performed to compare the general case and the limiting case of a prevailing Boltzmann distribution and to examine the influence of “slip“ and ”stick“ boundary conditions, as well as the isotropic diffusion.