Selective absorption in symmetric molecular nano-films

A microscopic theory of dielectric properties of symmetrical ultrathin molecular films, was formulated in bosonic and nearest-neighbor approximation. The dispersion law of harmonic exciton states were calculated using the method of two-time, temperature dependent Green´s functions. It has been shown that two types of excitations can be occur: bulk and surface exciton states. Exciton spectral weights and space distribution along the direction of broken symmetry were analyzed as well. Calculating dynamical permittivity by the single-pole Green´s functions it was shown that the threshold of light absorption can be moved along frequencies, changing the film thickness and the intensity of boundary perturbations. This can give a great contribution to practical ultrathin film engineering.