1 Evolution of Cluster Production with Fragmentation Degree
7
1.4 Conclusion
We have looked at the contribution of species which composed final partitions produced in the
58 Ni+
58 Ni reactions. Using Z max , the charge of the biggest fragment
of each event, as sorting observable, we have sample classes of events from evaporation to vaporization. We distinguish different behaviors depending on the species
understudied (
1,2,3 H and
3,4 He). Looking at the mass fraction, we observe that the
A > 4 contributions are framed by the lighter clusters contribution. The
4 He contribution is predominant whatever the underlying mechanism leading to final observed
partitions. The use of several beam energies allow to evidence the effect of cluster
production when multifragmentation occurs: at low beam energies, the energetic cost
to produce fragments freeze the production of light clusters. This contribution starts
to increase again for highest beam energies where the partitions may be produced
sufficiently excited to go through secondary decays. Using excitation energy E
∗ as
a second sorting observable, we show that cluster contributions are fully determined
whatever the beam energies. We observe also that the
4 He clusters are a good candidate to track the exploration of the phase diagram during the reaction process. These
results are coherent with a statistical description of fragment production which at
first order is conditioned by the excitation energy and the volume of the system as it
is foreseen in the freeze-Out picture of the (micro-)canonical statistical models.
References
1. B. Borderie, J.D. Franklanf, Liquid-Gas phase transition in nuclei. Prog. Part. Nucl. Phys. 105,
82–138 (2019) (and references therein)
2. B. Borderie et al., Phase transition dynamics for hot nuclei. Phys. Lett. B 782, 291–296 (2018)
3. E. Bonnet et al., Bimodal behavior of the heaviest fragment distribution in projectile fragmentation. Phys. Rev. Lett. 103, 072701 (2009)
4. J. Pouthas et al., INDRA, A 4 π charged product detection array at GANIL, Nucl. Instrum.
Methods Phys. Res. A 357, 418–442 (1995); J. Pouthas et al., The electronics of the INDRA 4π
detection array, Nucl. Instrum. Methods Phys. Res. A 369, 222–247 (1996)
5. E. Galichet et al., Isospin diffusion in Ni 58 -induced reactions at intermediate energies. I. Experimental results. Phys. Rev. C 79, 064614 (2009)
6. P. Lautesse et al., Evolution of the fusion cross- section for light systems at intermediate energies.
Eur. Phys. J. A 27, 349–357 (2006)
7. E. Bonnet, Evolution of cluster production with fragmentation degree. Nuovo Cimento della
Societa Italiana di Fisica C 41, 183 (2018)
8. E. Bonnet et al., Fragment properties of fragmenting heavy nuclei produced in central and
semi-peripheral collisions. Nucl. Phys. A 816, 1–18 (2009)
7
1.4 Conclusion
We have looked at the contribution of species which composed final partitions produced in the
58 Ni+
58 Ni reactions. Using Z max , the charge of the biggest fragment
of each event, as sorting observable, we have sample classes of events from evaporation to vaporization. We distinguish different behaviors depending on the species
understudied (
1,2,3 H and
3,4 He). Looking at the mass fraction, we observe that the
A > 4 contributions are framed by the lighter clusters contribution. The
4 He contribution is predominant whatever the underlying mechanism leading to final observed
partitions. The use of several beam energies allow to evidence the effect of cluster
production when multifragmentation occurs: at low beam energies, the energetic cost
to produce fragments freeze the production of light clusters. This contribution starts
to increase again for highest beam energies where the partitions may be produced
sufficiently excited to go through secondary decays. Using excitation energy E
∗ as
a second sorting observable, we show that cluster contributions are fully determined
whatever the beam energies. We observe also that the
4 He clusters are a good candidate to track the exploration of the phase diagram during the reaction process. These
results are coherent with a statistical description of fragment production which at
first order is conditioned by the excitation energy and the volume of the system as it
is foreseen in the freeze-Out picture of the (micro-)canonical statistical models.
References
1. B. Borderie, J.D. Franklanf, Liquid-Gas phase transition in nuclei. Prog. Part. Nucl. Phys. 105,
82–138 (2019) (and references therein)
2. B. Borderie et al., Phase transition dynamics for hot nuclei. Phys. Lett. B 782, 291–296 (2018)
3. E. Bonnet et al., Bimodal behavior of the heaviest fragment distribution in projectile fragmentation. Phys. Rev. Lett. 103, 072701 (2009)
4. J. Pouthas et al., INDRA, A 4 π charged product detection array at GANIL, Nucl. Instrum.
Methods Phys. Res. A 357, 418–442 (1995); J. Pouthas et al., The electronics of the INDRA 4π
detection array, Nucl. Instrum. Methods Phys. Res. A 369, 222–247 (1996)
5. E. Galichet et al., Isospin diffusion in Ni 58 -induced reactions at intermediate energies. I. Experimental results. Phys. Rev. C 79, 064614 (2009)
6. P. Lautesse et al., Evolution of the fusion cross- section for light systems at intermediate energies.
Eur. Phys. J. A 27, 349–357 (2006)
7. E. Bonnet, Evolution of cluster production with fragmentation degree. Nuovo Cimento della
Societa Italiana di Fisica C 41, 183 (2018)
8. E. Bonnet et al., Fragment properties of fragmenting heavy nuclei produced in central and
semi-peripheral collisions. Nucl. Phys. A 816, 1–18 (2009)