MOLECULAR FLUORESCENCE AT A ROUGH-SURFACE - THE ORIENTATION EFFECTS

The problem of the dynamical interaction between an emitting dipole an d a metallic grating surface is considered with particular interest in the effects due to different orientations of the dipole with respect to the substrate surface. Our previous perturbative theory is extended to treat both parallel and perpendicular dipoles and the results are applied to the study of modified fluorescence characteristics for admo lecules in the vicinity of a rough metal surface modeled as a grating. Numerical results show that some of the characteristics are very sens itive to the molecular orientation and the one along the grating direc tion is manifested with some unique behavior. The possibility of lengt hening molecular lifetimes at a patterned surface is indicated via the manipulation of the surface roughness as well as the orientations of the molecules. In addition, the limitation of the usual step in averag ing the theoretical results in the comparison with experimental measur ed values is pointed out.