Complete and incomplete fusion in the ${}^9\mathrm{Be}$ $+{}^{181}\mathrm{Ta}$ reaction

Complete and incomplete fusion cross sections for the ${}^9\mathrm{Be}$ $+{}^{181}\mathrm{Ta}$ system were measured at near barrier energies, using the offline gamma ray spectroscopy method. The results were compared with coupled channel calculations that do not take into account the coupling of the breakup channel, using a double folding potential as bare potential. A complete fusion suppression of the order of 35% was found, at energies above the barrier, whereas the total fusion cross sections are in agreement with the calculations. The ratio between incomplete fusion and total fusion at energies above the Coulomb barrier was found to be $32\pm 1\%$. At sub-barrier energies one observes some enhancement of total fusion cross section.

Figure 1

Typical $\gamma$-ray spectra obtained from offline measurement at the projectile energy of 44.7 MeV after 4 h (a) and 54 d (b) of irradiation of the ${}^{181}\mathrm{Ta}$ target with measuring times 1 h and 32 h, respectively. The 238.4, 583.0, 609.2, and 969.0 keV $\gamma$ peaks come from natural background radiation.

Figure 2

Experimental and predicted ratios of a given complete fusion $xn$ evaporation product to the sum of all such products for the ${}^9\mathrm{Be}$ $+{}^{181}\mathrm{Ta}$ reaction.

Figure 3

Model independent ratio of ICF/TF. The mean ratio at energies above the Coulomb barrier is represented by a shadow region. The stars represent the points at energies below and near $V_B$, not taken into account to find the mean value of ICF/TF, while the full circles represent the points used to determine the mean value of the ratio at energies above $V_B$.

Figure 4

Experimental CF and TF excitation functions (points) and theoretical predictions using a parameter free folding potential as bare potential and CC calculations including target inelastic excitations (see text for details).

Figure 5

Renormalized experimental complete and total fusion functions versus the dimensionless energy variable $x$, following the prescription of Ref. [39]. $x=0$ corresponds to the Coulomb barrier energy. The full curves are the universal fusion function (UFF) and the same curve multiplied buy the factor 0.65.