Irradiation of the water molecule by the femtosecond laser field

Abstract

By means of the time-dependent density functional theory (TDDFT) (applied to valence electrons), coupled with non-adiabatically molecular dynamics of ions, the excitation and dynamics of water molecules in a laser field with different polarizations have been explored. It is found that for the same polarization, the water molecule ionization can be enhanced with increasing laser intensity, while the laser intensity keeps constant, the ionization shows a maximum when the polarization is along the molecular symmetry axis, and the ionization is suppressed maximally when the polarization is perpendicular to the symmetry axis of the water molecule. The study of the dipole moment indicates that when the molecule is in the linear response region, there is only the oscillation of Dx for the case of the polarization along the x axis, while there is only the oscillation of Dy for the case of the polarization along the y axis. The bond lengths and the bond angle of H2O molecules are enlarged, while their may ictudes decrease with increasing polarization angle. Furthermore, it is found that in different polarization cases the vibration frequency of OH bonds is almost the same as the laser frequency during the action of the laser field, and it decreases after the laser pulse is switched off; however, the vibration mode of H2O molecule is sensitive to the laser polarization.