Nonlinear response ofs olids and molecules in intense infrared radiation

摘要

Infrared radiation, which couples with vibrations in molecules and solids, has long been con-sidered as a promising way to selectively control chemical reactions, materials processing, and biomedical applications. The expectation is that particular frequencies couple to speciific atomic motions, in contrast to ehat which imparts energy indiscriminately. The promise has yet to be fulfilled, but recent successes and the development of new lasers have rekindled interest. We report calculations of the dynamics of soids and molecules under intense infrared radiation. In solids, using a model calculation, we fnd that narrowly-defiined "windows of opportunity" exist for resonant enhancement of impurity diffusion at moderate intensities. In molecules, using a generalization of Car-Parrinello dynamics, we find that, for very intense fields, energy absorption at normal modes is not very efficient and that selective bond-breaking may occur at nonresonant frequencies by "concerted kicks". Finally, time-dependent density functional toeyr is used to show that the effect of very intense infrared radiation on atoms and molecules is to produce very high harmonics as found experimentally.