POLARIZED FLUORESCENCE SPECTROSCOPY OF 2-GROUND-STATE AND 2-EXCITED-STATE SYSTEMS IN SOLUTIONS

The polarized fluorescence spectroscopy of two-ground and two-excited state systems in solution is discussed. A state-dependent diffusion mo del for the rotational motion of an asymmetric, symmetric and spherica l rotor is considered. Analytic expressions for the polarized fluoresc ence components in the case of symmetric and spherical diffusors are d erived. The absorption and emission transition dipole moments have dif ferent directions in the molecule-fixed frames in both ground- and exc ited-state species. The case of double absorption bands with different directions of absorption dipole moments, in both ground-states specie s, is discussed. The problem of convolution between the instrument res ponse function with a model decay is also discussed. Two methods for r ecovering the instrument response function are considered; namely, the scatter method and the method of a monoexponential reference compound . The theory discussed in this work can be employed to many problems i mportant from an experimental point of view e.g., different kinds of e xcited-state reactions or excitation energy transfer in rigid double-c hromophore complexes. Computer generated synthetic decays of polarized fluorescence and emission anisotropy for the one-ground- and two-exci ted-state problem are exemplified.