Near-resonant absorption in the time-dependent self-consistent field and multiconfigurational self-consistent field approximations

Abstract

The linear response function has been derived and implemented in the time-dependent self-consistent field and multiconfigurational self-consistent field approximations with consideration made for the finite lifetimes of the electronically excited states. Inclusion of damping terms makes the response function convergent at all frequencies including near-resonances and resonances. Applications are the calculations of the electric dipole polarizabilities of hydrogen fluoride, methane, trans-butadiene, and three push–pull systems. The polarizability is complex with a real part related to the refractive index and an imaginary part describing linear absorption. The relevance of linear absorption in nonlinear optics is effectively expressed in terms of figures-of-merit. Such figures-of-merit have been calculated showing that the nonresonant linear absorption must be considered when the nonlinear optical quality of a material is to be assessed.