  The present work aims to investigate the effect of individual rotational
energy levels on the fusion cross-sections for $^{16}$O-based reaction systems,
namely, $^{16}$O + $^{182,184,186}$W, $^{16}$O + $^{176,180}${Hf}, $^{16}$O +
$^{174,176}${Yb}, $^{16}$O + $^{166}${Er}, $^{16}$O + $^{148,152,154}$Sm,
$^{16}$O + $^{150}$Nd at energies below the fusion barrier. Using the CCFULL
code, the effect of low-lying rotational energy levels on the fusion
cross-section for $^{16}$O induced reactions has been investigated at energies
below and around the Coulomb barrier. The calculations are performed by
assuming the fixed value of diffuseness parameter $a_{0}=0.65$ fm in the
Woods-Saxon nuclear potential and the other two parameters are optimised by
fitting the experimental data at the above barrier. Here we have determined the
$V_0$ and $r_0$ as a function of $Z_PZ_T$, where experimental cross-sections
are available. From our calculations, it is observed that the hexadecapole
deformation ($\beta_4$) with different magnitudes has a significant influence
on the fusion cross sections. For the case of the $+ve$ value of $\beta_4$,
beyond $10^+$, the rotational levels cease to contribute significantly and also
there is a significant difference between the contribution of sequential
channels. On the other hand, in the case of -ve $\beta_4$, up to $6^+$ levels
contribute significantly. Furthermore, we have established an algebraic
systematic of fitting, which one can use to determine the parameters $V_0$,
$r_0$ of Woods-Saxon nuclear potential within the range of $Z_PZ_T$ lie in
between $480 \le {Z_PZ_T} \le 592$.
