Quasiprojectile and intermediate velocity isotopic ratios for light fragments emitted in the ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$ and ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$ reactions between $32A$ and $84A$ MeV

Isotopic ratios for light fragments ($Z\le 4$) emitted by the quasiprojectile (QP) and the mid-rapidity (MR) sources are investigated by the use of a slightly asymmetric system (${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$) and a symmetric one (${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$) for six energies between 32A and 84A MeV and three semiperipheral centrality range selections. Experimental data come from the INDRA $4\pi$ multidetector. The results show a clear neutron-rich isotope production from the MR region as compared to the QP source. The beam energy and the centrality also show interesting different trends depending on the charge of the fragments and the emission source. Experimental results are compared to antisymmetrized molecular dynamics simulations.

Figure 1

Total charge as a function of the pseudomomentum for the ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$ reaction at 40A MeV.

Figure 2

(a) $b$ as a function of $b_{\exp }$ for the ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$ reaction at 52A MeV simulated by using HIPSE (no filter). (b) Gaussian fit on the $b_{\exp }-b$ distribution.

Figure 3

The three selected regions of the experimental impact parameter ($b_{\exp }$) for ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$ (a) and ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$ (b) reactions at 52A MeV.

Figure 4

Estimation of the QP rapidity for ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$ at 52A MeV. See text for details.

Figure 5

${}^4\mathrm{He}$ source selection by using the statistical method for ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$ at 52A MeV in the $7<b_{\exp }<7.5$ region. The “Mass_ID=0” region corresponds to unresolved masses.

Figure 6

Experimental $N/Z$ of H (a) and He (b) isotopes as a function of the beam energy for ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$. Closed (open) symbols correspond to the QP (MR source). The three selected centrality regions are also shown. ${}^1\mathrm{H}$ results are not included. Lines serve to guide the eye.

Figure 7

Experimental $N/Z$ of H (a) and He (b) isotopes as a function of the beam energy for ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$. Closed (open) symbols correspond to the QP (MR source). The three selected centrality regions are also shown. ${}^1\mathrm{H}$ results are not included. Lines serve to guide the eye.

Figure 8

Experimental $N/Z$ of Li (a) and Be (b) isotopes as a function of the beam energy for ${}^{36}\mathrm{Ar}+{}^{58}\mathrm{Ni}$. Closed (open) symbols correspond to the QP (MR source). The three selected centrality regions are also shown. ${}^8\mathrm{Be}$ results are not included. Lines serve to guide the eye.

Figure 9

Experimental $N/Z$ of Li (a) and Be (b) isotopes as a function of the beam energy for ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$. Closed (open) symbols correspond to the QP (MR source). The three selected centrality regions are also shown. ${}^8\mathrm{Be}$ results are not included. Lines serve to guide the eye.

Figure 10

Total $N/Z$ ratio as a function of the energy of the ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$ reaction at 32A, 52A, and 82A MeV simulated by using AMD (no filter). Closed (open) symbols correspond to the QP (MR source). Four centrality regions are also shown. Lines serve to guide the eye.