arXiv subjects

C. Bertulani

Publications and source records attributed to C. Bertulani.

7 recordsLinked to original sources

arXiv2023

New 26P(p,γ)27S thermonuclear reaction rate and its astrophysical implication in rp-process

Accurate nuclear reaction rates for 26P(p,γ)27S are pivotal for a comprehensive understanding of rp-process nucleosynthesis path in the region of proton-rich sulfur and phosphorus isotopes. However, large uncertainties still exist in the current rate of 26P(p,γ)27S because of the lack of the nuclear mass and the energy level structure information of 27S. We reevaluate this reaction rate using the experimentally constrained 27S mass, together with the shell-model predicted level structure. It is found that the 26P(p,γ)27S reaction rate is dominated by a direct-capture (DC) reaction mechanism despite the presence of three resonances at E = 1.104, 1.597, 1.777 MeV above the proton threshold in 27S. The new rate is overall smaller than the other previous rates from Hauser-Feshbach statistical model by at least one order of magnitude in the temperature range of X-ray burst interest. In addition, we consistently update the photodisintegration rate using the new 27S mass. The influence of new rates of forward and reverse reaction in the abundances of isotopes produced in rp-process is explored by post-processing nucleosynthesis calculations. The final abundance ratio of 27S/26P obtained using the new rates is only 10% of that from the old rate. The abundance flow calculations show the reaction path 26P(p,γ)27S(\b{eta}+,ν)27P is not as important as thought previously for producing 27P. The adoption of the new reaction rates for 26P(p,γ)27S only reduces the final production of aluminum by 7.1%, and has no discernible impact on the yield of other elements.

nucl-th↗

arXiv2015

Relativistic Coulomb excitation within Time Dependent Superfluid Local Density Approximation

Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus $^{238}$U. The approach is based on Superfluid Local Density Approximation (SLDA) formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We have computed the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, the dipole pygmy resonance and giant quadrupole modes were excited during the process. The one body dissipation of collective dipole modes is shown to lead a damping width $Γ_\downarrow \approx 0.4$ MeV and the number of pre-equilibrium neutrons emitted has been quantified.

nucl-th↗

arXiv2014

Big-Bang Nucleosynthesis verifies classical Maxwell-Boltzmann distribution

We provide the most stringent constraint to date on possible deviations from the usually-assumed Maxwell-Boltzmann (MB) velocity distribution for nuclei in the Big-Bang plasma. The impact of non-extensive Tsallis statistics on thermonuclear reaction rates involved in standard models of Big-Bang Nucleosynthesis (BBN) has been investigated. We find that the non-extensive parameter $q$ may deviate by, at most, $|δq|$=6$\times$10$^{-4}$ from unity for BBN predictions to be consistent with observed primordial abundances; $q$=1 represents the classical Boltzmann-Gibbs statistics. This constraint arises primarily from the {\em super}sensitivity of endothermic rates on the value of $q$, which is found for the first time. As such, the implications of non-extensive statistics in other astrophysical environments should be explored. This may offer new insight into the nucleosynthesis of heavy elements.

astro-ph.CO↗

arXiv2013

Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.

astro-ph.IM↗

arXiv2012

Medium effects in direct reactions

We discuss medium corrections of the nucleon-nucleon (NN) cross sections and their influence on direct reactions at intermediate energies $\gtrsim 50$ MeV/nucleon. The results obtained with free NN cross sections are compared with those obtained with a geometrical treatment of Pauli-blocking and with NN cross sections obtained with Dirac-Bruecker methods. We show that medium corrections may lead to sizable modifications for collisions at intermediate energies and that they are more pronounced in reactions involving weakly bound nuclei.

nucl-th↗

arXiv2004

$g_{s}$-factor quenching with quantum statistics

We discuss the effect of quantum statistics on the $g_{s}$-factor quenching in nuclear medium. We have found that the two nucleon correlation function can be described by a Gaussian with correlation length $σ\sim1.2$ fm. An estimate of the M1 quenching strength is given. The effect of quantum statistics on the retardation of the paramagnetic susceptibility is also discussed.

hep-ph↗

arXiv1994

Coherent Bremsstrahlung Emission in the Early Stage of Relativistic Heavy Ion Collisions

We present a model of coherent Bremsstrahlung emission from the compression phase of relativistic heavy ion collisions based on a hydrodynamical description of the collision process. The decceleration of the matter through a shock front, calculated in 1-D relativistic dissipative hydrodynamics, is at the origin of a copious Bremsstrahlung emission. The interferences between the Bremsstrahlung emitted by two receeding shock fronts result in deviations from the usual $1/ω$ law, with in particular a strong suppression of low energy photons in symmetric collisions. We show how it might be possible to obtain information on the equation of state, possible transition to a quark gluon plasma and dynamical properties of the matter from the study of the interference pattern. We show that the optimal region for the observation of coherent photons is in SIS - AGS energy range.

hep-ph↗