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

The linear response function has been derived and implemented in the time-d ependent self-consistent field and multiconfigurational self-consistent fie ld approximations with consideration made for the finite lifetimes of the e lectronically excited states. Inclusion of damping terms makes the response function convergent at all frequencies including near-resonances and reson ances. Applications are the calculations of the electric dipole polarizabil ities of hydrogen fluoride, methane, trans-butadiene, and three push-pull s ystems. The polarizability is complex with a real part related to the refra ctive index and an imaginary part describing linear absorption. The relevan ce of linear absorption in nonlinear optics is effectively expressed in ter ms of figures-of-merit. Such figures-of-merit have been calculated showing that the nonresonant linear absorption must be considered when the nonlinea r optical quality of a material is to be assessed. (C) 2001 American Instit ute of Physics.