Comprehensive study of reaction mechanisms for the ${}^9\mathrm{Be}+{}^{144}\mathrm{Sm}$ system at near- and sub-barrier energies

The delayed x-ray detection technique was used to measure complete and incomplete fusion cross sections for the ${}^9\mathrm{Be}+{}^{144}\mathrm{Sm}$ reaction at sub- and near-barrier energies. Elastic and inelastic scattering for this system were also measured. Reaction cross sections were derived and the transfer cross sections of one neutron were calculated. The suppression of complete fusion above the barrier, of the order of 10%, is attributed to ${}^9\mathrm{Be}$ breakup and is considerably smaller than the value of 30% found for the ${}^9\mathrm{Be}+{}^{208}\mathrm{Pb}$ system.

Figure 1

Schematic diagrams of reaction mechanisms (a) involving any kind of nuclei and (b) involving weakly bound nuclei.

Figure 2

Schematic diagrams of particular reaction mechanisms involving ${}^9\mathrm{Be}$ as a projectile.

Figure 3

Predictions of the evaporation code PACE for the evaporation following the complete fusion of ${}^9\mathrm{Be}+{}^{144}\mathrm{Sm}$, using level density parameter $A/8$.

Figure 4

Decay scheme of the CF and ICF compound nuclei.

Figure 5

$K_{\alpha }$ x-ray spectra taken from (a) 5-mins run taken a few minutes after the end of the irradiation and (b) 30-mins run taken 90 mins after the end of the irradiation.

Figure 6

Elastic scattering angular distributions. The dashed lines correspond to the São Paulo potential predictions without any fit, whereas the full lines correspond to the fits using one normalization factor for the real and one for the imaginary parts of the São Paulo potential. For the highest energies, there was no need to change the standard parameters.

Figure 7

Ratios for each evaporation channel cross section/CF cross section, as a function of the energy.

Figure 8

CF evaporation channels and ICF excitation functions.

Figure 9

Measured and derived cross sections obtained in this work: CF, ICF, reaction, inelastic, and DR. See text for details.

Figure 10

Ratio of ${\sigma }_{\mathrm{ICF}}/{\sigma }_{\mathrm{TF}}$ as a function of the energy divided by the average barrier energy, assuming that all ${}^{147}\mathrm{Gd}$ originate from ICF. The line represents an average suppression factor.

Figure 11

Experimental lower limits of CF and TF cross sections (open points and full points, respectively) and CC calculation results when excited states of Sm, the Be ground-state rotational band couplings, and $1n$ transfer are included. The CF suppression at energies above the barrier is derived to be 10%.

Figure 12

Calculated $1n$ transfer cross section for the ${}^9\mathrm{Be}+{}^{144}\mathrm{Sm}$ system and, for comparison, the measured CF and ICF cross sections.

Figure 13

Ratios between the individual cross sections and the reaction cross section as a function of reduced energy. The derived ${\sigma }_{\mathrm{NCBU}+\alpha \mathrm{transfer}}$ is obtained by subtracting from ${\sigma }_R$ the measured ${\sigma }_{\mathrm{TF}}+{\sigma }_{\mathrm{inelastic}}($${}^{144}\mathrm{Sm}$) + calculated ${\sigma }_{1n\mathrm{transfer}}$.