Two-photon-excitation fluorescence depolarization in solutions and nano-scale-organized (macro)molecular media: Application of the wide-angular detection-aperture technique
Issue title: Atomic and molecular nonlinear optics: Theory, Experiment and Computation A homage to the pioneering work of Stanisław Kielich (1925-1993)
Guest editors: G. Maroulis, T. Bancewicz, B. Champagne and A.D. Buckingham
Affiliations: [a] Institute of Physics, Nicholaus Copernicus University, ul. Grudziádzka 5/7, PL 87-100 Toruń, Poland | [b] Department pf Physics and Biophysics, Unversity of Warmia and Mazury, Olsztyn, Poland
Abstract: We here discuss a problem of time-resolved fluorescence polarization spectroscopy at two-photon excitations of macroscopically isotropic molecular media, that can be organized locally on a nano-scale. The simplifying assumptions on the hydrodynamical shape of fluorophores and on the form of the two-photon absorption tensor, are considered and displayed on the corresponding examples of the emission anisotropy synthetic decays. These assumptions reduce the number of the model parameters making the theoretical description of the discussed spectroscopic technique applicable in the experimental practice. Because the two-photon excitations of fluorescence require the application of the exciting light of appropriately high intensity, and that may have a negative influence on the quality of the experimental data collected, we discuss the application of the wide-angular detection-aperture technique in such experiments. Furthermore, we consider the application of the symmetry adapted callibration (SAC) method enabling one to accurately analyze the experimental data even if the collecting optics employed is not ideal and is affected by several unexpected technical imperfections that are hard to be accounted for analytically.
