Nuclear level densities of ${}^{64,66}$Zn from neutron evaporation

Double differential cross sections of neutrons from $d+{}^{63,65}$Cu reactions have been measured at deuteron energies of 6 and 7.5 MeV. The cross sections measured at backward angles have been compared to theoretical calculations in the framework of the statistical Hauser-Feshbach model. Three different level density models were tested: the Fermi-gas model, the Gilbert-Cameron model, and the microscopic approach through the Hartree-Fock-Bogoliubov method (HFBM). The calculations using the Gilbert-Cameron model are in best agreement with our experimental data. Level densities of the residual nuclei ${}^{64}$Zn and ${}^{66}$Zn have been obtained from statistical neutron evaporation spectra. The angle-integrated cross sections have been analyzed with the exciton model of nuclear reaction.

Figure 1

Double differential cross sections in the center-of-mass frame of ${}^{63}$Cu($d,n$) for deuteron energies of (a) 6 and (b) 7.5 MeV and ${}^{65}$Cu($d,n$) for (c) 6 and (d) 7.5 MeV. The error bars represent statistical errors only. The cross section from each angle is scaled down by a factor of 0.1 as the angle is increased.

Figure 2

Angular distributions of (a) ${}^{63}$Cu($d,n$) and (b) ${}^{65}$Cu($d,n$) for incident deuteron energy of 6 MeV taken from selected neutron energy intervals. The solid line is a fit from the Kalbach formula given in Eq. (2).

Figure 3

Experimental differential cross sections compared to theoretical calculations using different input level density models for (a) ${}^{63}$Cu($d,n$) and (b) ${}^{65}$Cu($d,n$) for the 6-MeV incident deuteron energy.

Figure 4

Differential cross sections obtained with the 7.5-MeV incident energy for ${}^{63}$Cu($d,n$) (top) and ${}^{65}$Cu($d,n$) (bottom) (a factor of 0.01 was used for distinction). The predictions were calculated based on the best GCM parameters found in Table .

Figure 5

Level density versus the excitation energy for (a) ${}^{64}$Zn and (b) ${}^{66}$Zn. The data for 6-MeV incident energy (square) and 7.5 MeV (circle) were normalized to the discrete low lying levels (histogram). The experimental level densities were compared to the NLD models: FGM (dashed-dotted red line) with Egidy parameters systematics [3] and GCM (dashed blue line) with parameters systematics according to Ref. [17] and Ref. [4] for ${}^{64}$Zn and ${}^{66}$Zn, respectively.

Figure 6

Experimental angle-integrated differential cross sections for ${}^{65}$Cu($d$,Xn) at energies (a) 6 and (b) 7.5 MeV. Solid lines are empire and talys calculations. PE and comp stand for pre-equilibrium and compound components, respectively. The red solid line has its mean free path set to 1.3, which is the default value while the black solid line has it set to 0.5.