The interaction of intense femtosecond laser pulses with rare gas clusters was studied experimentally, the time-of-flight spectra of ions from exploding clusters at different gas densities have been measured. It is found that while the relative components of ions in low and high energy of the ion energy spectrum decrease with the increase of the gas density, the average ion energies are the same for different gas densities， which indicates that the effect of gas density on laser-cluster interaction is not important under our experimental conditions.
The geometries of hyperlithiated compounds OLin were optimized by means of HF, MP2 and DFT methods with 6-31G basis set. The dissociation energies of those optimized stable geometries of OLin were calculated, the results are in good agreement with experimental values; and moreover, the dissociation energy of OLi6 is predicted. In addition, the fundamental vibrational frequencies were also predicted.
