We propose a method to obtain adiabatic internuclear potentials via energy
variation with the intercluster-distance constraint. The adiabatic 16O +
16,18O potentials obtained by the proposed method are applied to
investigate the effects of valence neutrons in 16O + 18O sub-barrier
fusions. Sub-barrier fusion cross sections of 16O + 18O are enhanced
more compared to those of 16O + 16O because of distortion of valence
neutrons in 18O.Comment: 11 pages, 5 figure