Angle-dependent irradiation of C₄ in femtosecond laser pulses

We study the angle-dependent irradiation of linear C₄ in the strong femtosecond laser pulses with the help of time-dependent local density approximation applied to valence electrons, coupled non-adiabatically to molecular dynamics of ions. It is found that the excitation of C₄ including the electrons and ions has a strong relation to the angle between the laser polarization and the internuclear axis of C₄. The ionization yield decreases when the angle ranges from 0 to π/2. A clear suppression in the ionization yield is found when the laser polarization is perpendicular to the internuclear axis of C₄. We track the dynamic motion of ionized C₄ even in the relaxation time. It shows that the ionized C₄ keeps on oscillating without fragmenting after the irradiation in different cases, while it is more excited when the laser polarization is along the internuclear axis. Furthermore, it is found that the change of the ELF takes place mainly in the xy plane and xz plane and the electron ejection mainly comes from the middle two atoms for the θ = 0 case. (authors)