Isospin diffusion in binary collisions of S32+Ca40,48 and

Abstract

The systems 32 S + 40,48 Ca and 32 S + 48 Ti at 17.7 MeV/nucleon were investigated with the setup general array for fragment identification and for emitted light particles in dissipative collisions (GARFIELD) plus ring counter (RCo) at Laboratori Nazionali di Legnaro (LNL) of Istituto Nazionale di Fisica Nucleare (INFN). Fusion evaporation (FE), fusion fission (FF), and deep inelastic (DIC) events were identified, also through the comparison with the prediction of a transport model (stochastic mean field, SMF), coupled to GEMINI++ as an afterburner. This work mainly deals with the study of isospin transport phenomena in DIC events. In particular, the isospin diffusion is highlighted by comparing the average isotopic content of the quasiprojectile (QP) remnants observed when the target is the N = Z nucleus 40 Ca and when it is the neutron-rich 48 Ca. Also, the d/p and t/p ratios for particles forward emitted with respect to the QP were found to increase with increasing N/Z of the target.

Isospin transport phenomena for the systems Kr80+Ca40,48 at 35 MeV/nucleon

“…This indicates that in the investigated charge region (between 19 and 25) the N /Z of the QP residue for the 80 Kr + 48 Ca reaction is systematically higher by about 0.02 (i.e., less than 0.5 neutrons) than for 80 Kr + 40 Ca. This gives a direct evidence of isospin diffusion, as shown in the literature either on data collected with a spectrometer [10] (in this case covering all the QP residue charge range) or for a much lighter projectile [13].…”

“…No sensitivity to the symmetry energy density dependence was found in Ref. [13] at lower beam energy (17.7 MeV/nucleon) looking at the N /Z vs. Z of the QP; in this case the adopted model was again SMF followed by GEMINI++ [28]. This time the lack of sensitivity was expected, because below 20 MeV/nucleon the system is supposed to stay close to normal density.…”

Isospin diffusion measurement from the direct detection of a quasiprojectile remnant

“…5(a)) with a gap with respect to the symmetric reference (green solid triangles in fig. 5(a)) increasing towards central collisions, as the result of the interaction with a n-deficient partner so that the two colliding nuclei tend to equilibrate their N/Z ratios [51,62,63]. Remarkably, very similar observations can be repeated for the QP B channel, where the same hierarchy and evolution are evident.…”

Comparison of AMD calculations with experimental data for peripheral collisions of 93Nb+93Nb,116Sn at 38 MeV/nucleon

“…In fact isospin transport phenomena, related to the isospin gradient between target and projectile (isospin diffusion [44,45]) or to the density gradient between QP-QT (which are both at normal density) and the more diluted midvelocity zone (isospin drift [45]) have been observed in several experiments (see, e.g., Refs. [46][47][48][49][50][51][52][53]). Of course, some sensitivity to the effects of an asystiff or asy-soft interaction in the AMD calculations may be expected only for mass-resolved light particles.…”