Phenomenological and Microscopic Description of Molecular Layer and Crystal Optical Polarization

摘要

The optical polarization of molecular layers and crystals in the strong field is characterized by nonlinear susceptibilities (NSC), which are obtained from hyperpolarizabilities (HP) of free molecules in any order. NSC, distinct in layer and bulk, are also described at the microscopic level by means of inclusion of the Madelung interaction potential (MIP) into the Hartree-Fock equations (HFE) for molecular crystal. The phenomenological approach is deduced from the microscopic one, in particular, the known Bloembergen formula and χ(ω) = α(ω)(ν-α(ω)L)~(-1) are derived from HFE for crystal HP. The calculations demonstrate that NSC, computed by both methods for fullerene crystal, coincide at all frequencies. Small deviations are determined by the anisotropy of the Madelung polarization interaction (MPI), which is expressed through the Lorentz tensor in the 2nd order in inter-electron distances. MPI anisotropy in cubic cell appears in the 4th order.