by $V_{pol}$ of (\[VP\]) with d=0.93 and of (\[VPExp-e\]) have very small values. This fact explains the small differences between DDCS’s with (\[VPExp-e\]) and without polarization potential observed in Figures (\[fig1\])-(\[fig3\]) (c) and (d). It is also obvious that deviations in $\delta_{pol}$ and so in $V_{pol}$ are manifested in the DDCS in the large $\eta$ region. This can be observed in Figure (\[fig5\]) where the DDCS evaluated with different forms of $V_{pol}$ is presented for O$^{8+}$ + Li(2s) collsions for $E_e$=2 eV.

In [@WW2014] ionization of Li was discussed within the framework of the coupled pseudostate (CP) model. Their results show similar good agreement with the measurement as the present ones at low and medium $\eta$ values when the shapes of the DDCS’s are considered. A similar study within the framework of the time-dependent close-coupling (TDCC) method was performed for $O^{8+}$ impact only in [@Ciappina13]. Reasonable agreement, especially for the Li(2p) target was observed. Results of these calculations are not included in Figures (\[fig1\])-(\[fig3\])) for the sake of clarity. However, in Figures (\[fig5-a\]) and (\[fig6\]) we give a comparison of the present, the CC, and the TDCC results for some selected collision parameters. In Figure (\[fig5-a\]) we compare the present DDCS results for O$^{8+}$ + Li(2s) collisions at $E_e$=2 eV with the CP and the TDCC results. The DDCS from the TDCC calculation is normalized to the present data at $\eta$=0.65 a.u. while those from the CP is shown on an absolute scale. In [@WW2014] the polarization potential was given by (\[VPExp\]) and the agreement between their and our results obtained with $V_{pol}$ of (\[VPExp\]) is good except around $\eta$=2 a.u. In [@Ciappina13] the NN interaction was taken into account by the Coulomb repulsion with an effective charge and those results seem to be comparable to our results without $V_{pol}$.

Similarly good agreement between our and the CP results of [@WW2014] can be observed in Figure (\[fig6\]) showi