Dynamical behavior of ultrashort pulse laser in para-nitroaniline molecules

Abstract

The electronic structures and dipole moments of para- nitroaniline molecule are calculated by use of density functional theory at ab initio level. We then inve stigate theoretically the interaction between the ultrashort pulse laser and the para-nitroaniline molecule medium by solving the full Maxwell-Bloch equations. The effects of permanent dipole moments on the pulse reshaping, the spectrum com ponents, and the evolutions of energy state populations are discussed in detail. The results show that the standing slowly varying envelope and the rotating-wav e approximations fail to give a good description for the propagation of an ultra short pulse in the molecule medium. Furthermore, the dipole moments of the molec ule make the propagation deviate from the area theorem further and make the pul se split more quickly. When the pulse with the excitation energy of the charge-t ransfer state propagates in the para-nitroaniline molecule medium, the second-ha rmonic spectral component appears obviously and becomes stronger as the propagat ing distance increases, which displays the high two-photon absorption properties of the molecule.