Theoretical approach to photoinduced inhomogeneous anisotropy in bacteriorhodopsin films

The aim of this work was to perform a complete study of the dynamic and steady-state photoinduced processes of thick bacteriorhodopsin (bR) films, taking into account all the physical parameters and the coupling of rate equations with the energy transfer equation. The theoretical approach was compared with experimental data, and good concordance was found between both sets of data. The theoretical approach shows that the values of the rate constants for solid bR films are about two or three orders of magnitude lower than those observed in solution. It can also be noted that the temperature change during the experiment had a great influence on the final values of transmittance and, consequently, on the inhomogeneous distribution along the coordinate of light propagation. The study shows that, depending on the intensity and wavelength of the pump beam, we can obtain a very inhomogeneous profile of the population densities, which implies an inhomogeneous profile of the birefringence and dichroism. Therefore, this must be taken into account in the applications described for this system.