Experimental study of precisely selected evaporation chains in the decay of excited Mg25

Abstract

The reaction 12 C + 13 C at 95 MeV bombarding energy is studied using the GARFIELD + Ring Counter apparatus located at the INFN Laboratori Nazionali di Legnaro. In this paper we want to investigate the de-excitation of 25 Mg aiming both at a new stringent test of the statistical description of nuclear decay and a direct comparison with the decay of the system 24 Mg formed through 12 C+ 12 C reactions previously studied. Thanks to the large acceptance of the detector and to its good fragment identification capabilities, we could apply stringent selections on fusion-evaporation events, requiring their completeness in charge. The main decay features of the evaporation residues and of the emitted light particles are overall well described by a pure statistical model; however, as for the case of the previously studied 24 Mg, we observed some deviations in the branching ratios, in particular for those chains involving only the evaporation of α particles. From this point of view the behavior of the 24 Mg and 25 Mg decay cases appear to be rather similar. An attempt to obtain a full mass balance even without neutron detection is also discussed.

Isospin diffusion measurement from the direct detection of a quasiprojectile remnant

“…In this paper one demonstrates, by means of the AMD simulation coupled with statistical models, that the charge equilibration process measured via isospin transport ratio is indeed affected by perturbations introduced by the dynamical and sta- tistical emissions from the fragments after their separation. In particular, the statistical emission (described by Gemini++ code) tends to introduce non-linear spurious distortions at low excitation energies (where structure effects are well known to affect the particle emission [67][68][69]), i.e. for large impact parameters, while the distortion becomes smoother and linear with increasing excitation.…”

Precise Study of Selected Evaporation Chains in Fusion Reactions Between Light Nuclei

“…For the sake of brevity, among the main findings reported elsewhere [6], we here underline two main results.…”

“…[5] or Fig. 3 of Ref [6]). A very similar mismatch has been previously found in the 12 C+ 12 C system [5], so one could wonder whether the additional neutron in the present 25 Mg case does not perturb so much the microscopic process (the fusion and the further decay), thus allowing some α-related effect to survive in the entrance channel and/or in the evaporative paths.…”

“…Here, we shortly discuss recent findings on the decay of excited 25 Mg nuclei, just adding only one neutron in the system, in order to see whether some differences with respect to statistical models, as found in the N = Z system, would survive (and to what extent) for 25 Mg nuclei, populated with comparable excitation energies (E * ≈ 60 MeV) and spins. The detailed description of this study is published elsewhere [6].…”

Influence of fast emissions and statistical de-excitation on the isospin transport ratio

“…The investigation of the causes behind the nonlinearity at low E * /A is out of the goal of this paper. A possible contribution could be due to structure effects, since is well known that they affect the particle emission at low excitation energy [42][43][44]. In this sense, the isoscaling analysis [4,5] could be more suited as it divides out many structure effects to the first order.…”