The ground states of PuO3 under different electric fields ranging from 0.005 to 0.005 a.u. have been optimized using density functional theory DFT/B3LYP with RECP for Pu and 6-311+G* for O. The excitation energies and oscillator strengths have been calculated under the same electric fields employing the time-dependent DFT method. The results show that the electronic state and excitation energy are strongly dependent on the field strength of applied electric field. The total energy of the ground state decreases linearly with the applied field strength. The dependence of the calculated excitation energies on the applied electric field strength is fitting well to the relationship proposed by Grozema. The excitation energies of the first five excited states of PuO3 decrease as the applied electric field increases because the energy gap between the HOMO and LUMO become close with the field

which shows that the molecule is easy to be excited under electric field and hence can be easily dissociated. The spectra of the first five-excited-electron of PuO3 are in the region of far infrared. The wavelength is in 900.2～2063.3 nm