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Register a new userAlpha-particle clustering in excited expanding self-conjugate nuclei
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The fragmentation of quasi-projectiles from the nuclear reaction 40Ca + 12C at 25 MeV/nucleon was used to produce alpha-emission sources. From a careful selection of these sources provided by a complete detection and from comparisons with models of sequential and simultaneous decays, strong indications in favour of $alpha$-particle clustering in excited 16O, 20Ne and 24}Mg are reported.
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The fragmentation of quasi-projectiles from the nuclear reaction $^{40}$Ca+$^{12}$C at 25 MeV per nucleon bombarding energy was used to produce $alpha$-emission sources. From a careful selection of these sources provided by a complete detection and from comparisons with models of sequential and simultaneous decays, evidence in favor of $alpha$-particle clustering from excited $^{16}O$, $^{20}Ne$ and $^{24}Mg$ is reported.
A theoretical approach was developed to describe secondary particle emission in heavy ion collisions, with special regards to pre-equilibrium {alpha}-particle production. Griffins model of non-equilibrium processes is used to account for the first stage of the compound system formation, while a Monte Carlo statistical approach was used to describe the further decay from a hot source at thermal equilibrium. The probabilities of neutron, proton and {alpha}-particle emission have been evaluated for both the equilibrium and pre-equilibrium stages of the process. Fission and {gamma}-ray emission competition were also considered after equilibration. Effects due the possible cluster structure of the projectile which has been excited during the collisions have been experimentally evidenced studying the double differential cross sections of p and {alpha}-particles emitted in the E=250MeV 16O +116Sn reaction. Calculations within the present model with different clusterization probabilities have been compared to the experimental data.
The fragmentation of quasi-projectiles from the nuclear reaction $^{40}Ca$+$^{12}C$ at 25 MeV/nucleon was used to produce excited states candidates to $alpha$-particle condensation. The methodology relies on high granularity 4$pi$ detection coupled to correlation function techniques. Under the assumption that the equality among the kinetic energies of the emitted $alpha$-particles and the emission simultaneity constitutes a reliable fingerprint of $alpha$ condensation, we identify several tens of events corresponding to the deexcitation of the Hoyle state of $^{12}$C which fulfill the condition.
The $alpha$ particle preformation in the even-even nuclei from $^{108}$Te to $^{294}$118 and the penetration probability have been studied. The isotopes from Pb to U have been firstly investigated since the experimental data allow us to extract the microscopic features for each element. The assault frequency has been estimated using classical methods and the penetration probability from tunneling through the Generalized Liquid Drop Model (GLDM) potential barrier. The preformation factor has been extracted from experimental $alpha$ decay energies and half-lives. The shell closure effects play the key role in the $alpha$ preformation. The more the nucleon number is close to the magic numbers, the more the formation of $alpha$ cluster is difficult inside the mother nucleus. The penetration probabilities reflect that 126 is a neutron magic number. The penetration probability range is very large compared to that of the preformation factor. The penetration probability determines mainly the $alpha$ decay half-life while the preformation factor allows us to obtain information on the nuclear structure. The study has been extended to the newly observed heaviest nuclei.
The fragmentation of quasi-projectiles from the nuclear reaction $^{40}$Ca+$^{12}$C at 25 MeV/nucleon was used to produce excited states candidates to $alpha$-particle condensation. Complete kinematic characterization of individual decay events, made possible by a high-granularity 4$pi$ charged particle multi-detector, reveals that 7.5$pm$4.0% of the particle decays of the Hoyle state correspond to direct decays in three equal-energy $alpha$-particles.
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