Our present studies has shown that the mass dependence of EVF show mass asymmetry independent behaviour. This is due the fact that with increase in asymmetry, the number of nucleon-nucleon collisions and repulsive Coulomb interactions decreases, therefore EVF increases. The increase in EVF with asymmetry is more for lighter nuclei as compared to heavier nuclei due to the further less magnitude of Coulomb repulsions in lighter nuclei as compared to heavier ones.
For the first time, the precise data on the above barrier fusion (capture) cross-sections for the reactions involving spherical colliding nuclei are quantitatively analyzed using the relativistic mean-field effective interaction. The parameter sets NL1, NL2, NL3, and HS are employed. The analysis is performed within the framework of the fluctuation-dissipation model with surface friction based on the double-folding approach for the nucleus-nucleus potential. The effective interactions, as well as the resulting potentials, are confronted with the ones obtained using the M3Y NN forces. Of the fo…
A recent article (D.A. Brown, et al., Phys. Rev. C98 024616 (2018)) rproposed a modification of the cross section formula used in practical calculations of compound nucleus reactions. We discuss the main concepts and approximations of statistical reaction theory and conclude that the standard practical implementations of the cross section formula remain the preferred choice.
A new model that includes the time-dependent dynamics of the single-particle (s.p.) motion in conjunction with the macroscopic evolution of the system is proposed for describing the compound nucleus (CN) formation in fusion of heavy nuclei. The diabaticity initially keeps the entrance system around its contact configuration, but the gradual transition from the diabatic to the adiabatic potential energy surface (PES) leads to fusion or quasifission. Direct measurements of the probability for CN formation are crucial to discriminate between the current models.
The total reaction cross section of high-energy nucleus-nucleus collision refects the nuclear density profiles of the colliding nuclei and has been a standard tool to investigate the size properties of short-lived unstable nuclei. This basis relies on the assumption that the nucleus-nucleus collision is strongly absorptive in the sense of an optical model. However, this property does not hold completely, while incomplete absorption occurs when an overlap density of two colliding nuclei is low enough. In this paper, we propose a way to quantify this incompleteness, that is, the "blackness" of t…
The understanding of the fusion probability is of particular importance to reveal the mechanism of producing superheavy elements. We present a microscopic study of the compound nucleus formation by combining time-dependent density functional theory, coupled-channels approach, and dynamical diffusion models. The fusion probability and compound nucleus formation cross sections for cold-fusion reactions $^{48}$Ca+$^{208}$Pb, $^{50}$Ti+$^{208}$Pb, and $^{54}$Cr+$^{208}$Pb are investigated and it is found that the deduced capture barriers, capture cross sections for these reactions are consistent w…
The entrance-channel mass-asymmetry dependence of the compound nucleus formation time in light heavy-ion reactions has been investigated within the framework of semiclassical dissipative collision models. the model calculations have been succesfully applied to the formation of the $^{38}$Ar compound nucleus as populated via the $^{9}$Be+$^{29}$Si, $^{11}$B+$^{27}$Al, $^{12}$C+$^{26}$Mg and $^{19}$F+$^{19}$F entrance channels. The shape evolution of several other light composite systems appears to be consistent with the so-called "Fusion Inhibition Factor" which has been experimentally observed…
The large body of experimental data on the fission fragments anisotropies are analyzed in several heavy-ion induced fission reaction systems. The entrance channel mass asymmetry parameters of these systems put on the both sides of the Businaro-Gallone mass asymmetry parameters. The role of the mass numbers of the projectile and the target in the prediction of a normal or an anomalous behavior in angular anisotropy, as well as the validity of standard saddle-point statistical model are considered. The average contribution of non compound nucleus fission for the systems with an anomalous behavio…
A statistical model description of heavy ion induced fusion-fission reactions is presented where shell effects, collective enhancement of level density, tilting away effect of compound nuclear spin and dissipation are included. It is shown that the inclusion of all these effects provides a consistent picture of fission where fission hindrance is required to explain the experimental values of both pre-scission neutron multiplicities and evaporation residue cross-sections in contrast to some of the earlier works where a fission hindrance is required for pre-scission neutrons but a fission enhanc…
A Multi-Channel Algebraic Scattering (MCAS) theory is presented with which the properties of a compound nucleus are found from a coupled-channel problem. The method defines both the bound states and resonances of the compound nucleus, even if the compound nucleus is particle unstable. All resonances of the system are found no matter how weak and/or narrow. Spectra of mass-7 nuclei and of {}^{15}F, and MCAS results for a radiative capture cross section are presented.
The semi-microscopic potential between heavy nuclei is evaluated for various colliding ions in the approach of frozen densities in the framework of the extended Thomas-Fermi approximation with hbar^2 correction terms in the kinetic energy density functional. The proton and neutron densities of each nucleus are obtained in the Hartree-Fock-BCS approximation with SkM* parameter set of the Skyrme force. A simple expression for the nuclear interaction potential between spherical nuclei is presented. It is shown that muon bound with light projectile induces the superheavy elements production in nuc…
We study the different nucleus-nucleus collisions, O+Au, S+S, S+Ag, S+Au and Pb+Pb, at the CERN-SPS energy in a one-fluid hydrodynamical approach using a parametrization based on baryon stopping in terms of the thickness of colliding nuclei. Good agreement with measured particle spectra is achieved. We deduce the mass number scaling behaviour of the initial energy density. We find that the equilibration time is nearly independent of the size of the colliding nuclei.
The possibility of synthesizing a doubly magic superheavy nucleus, $^{298}114_{184}$, is investigated on the basis of fluctuation-dissipation dynamics. In order to synthesize this nucleus, we must generate more neutron-rich compound nuclei because of the neutron emissions from excited compound nuclei. The compound nucleus $^{304}114$ has two advantages to achieving a high survival probability. First, because of small neutron separation energy and rapid cooling, the shell correction energy recovers quickly. Secondly, owing to neutron emissions, the neutron number of the nucleus approaches that …
The predictions of event anisotropy parameters from transport model RQMD are compared with the recent experimental measurements for 158$A$ GeV Pb+Pb collisions. Using the same model, we study the time evolution of event anisotropy at 2$A$ GeV and 158$A$ GeV for several colliding systems. For the first time, both momentum and configuration space information are studied using the Fourier analysis of the azimuthal angular distribution. We find that, in the model, the initial geometry of the collision plays a dominant role in determining the anisotropy parameters.
The evaporation residue yields from compound nuclei $^{220}$Th formed in the $^{16}$O+$^{204}$Pb, $^{40}$Ar+$^{180}$Hf, $^{82}$Se+$^{138}$Ba, $^{124}$Sn+$^{96}$Zr reactions are analyzed to study the entrance channel effects by comparison of the capture, fusion and evaporation residue cross sections calculated by the combined dinuclear system (DNS) and advanced statistical models. The difference between evaporation residue (ER) cross sections can be related to the stages of compound nucleus formation or/and at its surviving against fission. The sensitivity of the both stages in the evolution of…
Based on an extended compound nucleus model, isospin effects in statistical fragment emission from excited nuclear systems are investigated. An experimentally observed scaling behavior of the ratio of isotope yields $Y_i(N,Z)$ from two similar emitting sources with different neutron-to-proton ratios is predicted theoretically, i.e., the relationship of $Y_2/Y_1 \propto exp(αN + βZ)$ is demonstrated. The symmetry energy coefficient $C_{sym}$ extracted from the simulation results is $\sim$ 27 MeV which is consistent with realistic theoretical estimates and recent experimental data. The influence…
Using numerical holography, we study the collision of a planar sheet of energy with a bounded localized distribution of energy. The collision, which mimics proton-nucleus collisions, produces a localized lump of debris with transverse size $R \sim 1/T_{\rm eff}$ with $T_{\rm eff}$ the effective temperature, and has large gradients and large transverse flow. Nevertheless, the postcollision evolution is well described by viscous hydrodynamics. Our results bolster the notion that debris produced in proton-nucleus collisions may be modeled using hydrodynamics.
We present detailed results of a theoretical investigation on the production of evaporation residue nuclei obtained in a heavy ion reaction when charged particles (proton and $α$-particle) are also emitted with the neutron evaporation along the deexcitation cascade of the formed compound nucleus. The almost mass symmetric $^{82}$Se+$^{138}$Ba reaction has been studied since there are many experimental results on individual evaporation residue (ER) cross sections after few light particle emissions along the cascade of the $^{220}$Th compound nucleus (CN) covering the wide 12--70 MeV excitation …
We present an evidence of isospin effects in nuclear fission by comparing the fission widths for reactions involving different isospin states of the same compound nucleus (CN). Yadrovsky suggested this possibility in 1975. Yadrovsky obtained the fission widths for two reaction data sets, namely $^{206}$Pb($α$,f) and $^{209}$Bi(p,f), both leading to same CN, and concluded that "a nucleus remembers the isospin value of the nuclear states leading to fission". We obtain the fission decay widths for both the $T_0+1/2$ and $T_0-1/2$ states of CN by using two appropriate reaction data sets. We then c…
Saturation of small-x gluons in a nucleus, which has the form of transverse momentum broadening of projectile gluons in pA collisions in the nuclear rest frame, leads to a modification of the parton distribution functions in the beam compared with pp collisions. The DGLAP driven gluon distribution turns out to be suppressed at large x, but significantly enhanced at x<<1. This is a high twist effect. In the case of nucleus-nucleus collisions all participating nucleons on both sides get enriched in gluon density at small x, which leads to a further boosting of the saturation scale. We derive rec…
We extend a conventional description of the fusion-fission fragment angular distributions by introducing the correlation between compound nucleus states carrying different total angular momenta. This correlation results in the strong anisotropy and mass-angle correlation of fission fragments for compact saddle-point nuclear shapes for which the conventional description predicts almost isotropic angular distributions. The spin off-diagonal phase relaxation timescale, $\simeq 10^{-19}$ sec, obtained from analysis of anomalous fission fragment angular distributions in $^{12}$C+$^{236}$U, $^{16}$O…
The properties of deexcitation of the same $^{220}$Th compound nucleus (CN) formed by different mass (charge) asymmetric reactions are investigated. It is demonstrated that the effective fission barrier $<B_{\rm fis}>$ value being a function of the excitation energy $E^*_{\rm CN}$ is strongly sensitive to the various orbital angular momentum $L=\ell\hbar$ distributions of CN formed with the same excitation energy $E^*_{CN}$ by the very different entrance channels $^{16}$O+$^{204}$Pb, $^{40}$Ar+$^{180}$Hf, $^{82}$Se+$^{138}$Ba and $^{96}$Zr+$^{124}$Sn. Consequently, the competition between the …
The nuclear evaporation process is reformulated by taking into account simultaneous multiparticle emission from a hot compound nucleus appearing as an intermediate state in many nuclear reaction mechanisms. The simultaneous emission of many particles is particularly relevant for high excitation energy of the compound nucleus.These channels are effectively open in competition with the single particle emissions and fission in this energy regime. Indeed, the inclusion of these channels along the decay evaporating chain shows that the yield of charged particles and occurrence of fission are affect…
In this paper a role of many-nucleon dynamics in formation of the compound $^{5}{\rm Li}$ nucleus in the scattering of protons off $α$-particles at the proton incident energies up to 20 MeV is investigated. We propose a bremsstrahlung model allowing to extract information about probabilities of formation of such nucleus on the basis of analysis of experimental cross-sections of the bremsstrahlung photons. In order to realize this approach, the model includes elements of microscopic theory and also probabilities of formation of the short-lived compound nucleus. Results of calculations of the br…
The double folding (DF) approach is one of the widely used methods for finding nucleus-nucleus interaction potential. In the present work, the influence of the nuclear matter density on the DF potential and on the Coulomb barrier parameters is studied systematically for collisions of spherical nuclei. The value of the parameter $B_Z=Z_P Z_T/(A_P^{1/3}+A_T^{1/3})$ (estimating the Coulomb barrier height) varies in these calculations from 10 MeV up to 150 MeV. The novel feature of this study is that the nuclear densities came from the Relativistic Mean Field approach (RMF). For the nucleon-nucleo…
Investigations have shown that the collective motion not only appears in nucleus-nucleus but also in p-p collisions. The best tool for depicting such collective motion is relativistic hydrodynamics. In this paper, the collective motion is assumed obeying the hydro model which integrates the features of Landau and Hwa-Bjorken theory and is one of a very few analytically solvable models. The fluid is then supposed freezing out into charged particles from a time-like hypersurface with a fixed time of t_FO . The researches of present paper show that this part of charged particles together with lea…
The role of the entrance channel in fusion-fission reactions was studied by the theoretical analysis of the experimental evaporation residue excitation functions for reactions leading to the same compound nucleus. The evaporation residues cross sections for xn-channels were calculated in the frame of the combined dinuclear system concept and advanced statistical model. The revealed differences between experimental data on the evaporation residues in the ^{40}Ar+^{176}Hf, ^{86}Kr + ^{130}Xe and ^{124}Sn + ^{92}Zr reactions leading to the ^{216}Th^* compound nucleus are explained by the differen…
The Yang Mills equations provide a classical mean field description of gauge fields. In view of developing a coherent description of the formation of the quark gluon plasma in high energetic nucleus-nucleus collisions we study pure gauge field dynamics in 3+1 dimensions. In collisions of wave packets, numerically simulated on a SU(2) gauge lattice, we study transverse and longitudinal energy currents. For wave packets with different polarizations in color space, we observe a time delayed fragmentation after the collision resulting in a rapid expansion into transverse directions. We call this p…
The model for the cold-fusion reactions related to the synthesis of super-heavy nuclei in collisions of heavy projectile-nuclei with $^{208}$Pb target nucleus is discussed. In the framework of this model the production of the compound nucleus by two paths through, the di-nuclear system and the fusion way, are taken into account simultaneously. The formation of the compound nucleus in the framework of the di-nuclear system is related to the transfer of nucleons from the light nucleus to the heavy one. The fusion way is linked to the sequential evolution of the nuclear shape from the system of c…
Pre-saddle neutron multiplicity has been calculated for several fission reactions induced by heavy ions and light particles. Experimentally, it is impossible to determine the contribution of neutrons being emitted before the saddle point and those emitted between the saddle and the scission points. Determination of the pre-saddle neutron multiplicity in our research is based on the comparison between the experimental anisotropies and those predicted by the standard saddle-point statistical model. Analysis of the results shows that the pre-saddle neutron multiplicity depends on the fission barr…
Consideration of memory of spin and parity in the fissioning compound nucleus by applying the Hauser-Feshbach fission fragment decay model to photonuclear reactions
Calculations for fission and cluster decay of $^{76}Sr$ are presented for this nucleus to be in its ground-state or formed as an excited compound system in heavy-ion reactions. The predicted mass distribution, for the dynamical collective mass transfer process assumed for fission of $^{76}Sr$, is clearly asymmetric, favouring $α$-nuclei. Cluster decay is studied within a preformed cluster model, both for ground-state to ground-state decays and from excited compound system to the ground-state(s) or excited states(s) of the fragments.
The statistical model of compound-nucleus reactions predicts that the fluctuations of the partial $γ$-decay widths for a compound-nucleus resonance are governed by the Porter-Thomas distribution (PTD), and that consequently the distribution of total $γ$-decay widths is very narrow. However, a recent experiment [Koehler, Larsen, Guttormsen, Siem, and Guber, Phys. Rev. C 88, 041305(R) (2013)] reported large fluctuations of the total $γ$-decay widths in the $^{95}$Mo$(n,γ)^{96}$Mo* reaction, contrary to this expectation. Furthermore, in recent theoretical works it was argued that sufficiently str…
We present a Glauber-based study of J/Psi and Drell-Yan yields in nucleus-nucleus collisions. Using this approach, we have investigated the impact of energy loss by the colliding nuclei on observed yields and transverse momentum spectra of J/Psi and Drell-Yan. These studies permit an assessment of the importance of initial state energy loss in relation to "anomalous" J/Psi suppression.
Bayesian calibration of a regional optical potential and uncertainty-quantified predictions for compound nucleus reactions
University of Surrey（萨里大学）；Facility for Rare Isotope Beams, Michigan State University（密歇根州立大学稀有同位素束设施）；Department of Physics and Astronomy, Michigan State University（密歇根州立大学物理与天文学系）；AWE Nuclear Security Technologies（阿韦核安全技术有限公司）
Compound resonances in nucleon-nucleus scattering are related to the discrete spectrum of the target. Such resonances can be studied in a unified and general framework by a scattering model that uses sturmian expansions of postulated multichannel interactions between the colliding nuclei. Associated with such expanded multichannel interactions are algebraic multichannel scattering matrices. The matrix structure of the inherent Green functions not only facilitates extraction of the sub-threshold (compound nucleus) bound state spin-parity values and energies but also readily gives the energies a…
It is well established that physical systems exhibit both ordered and chaotic behavior. The chaotic behavior of nanostructure such as open quantum dots has been confirmed experimentally and discussed exhaustively theoretically. This is manifested through random fluctuations in the electronic conductance. What useful information can be extracted from this noise in the conductance? In this contribution we shall address this question. In particular, we will show that the average maxima density in the conductance is directly related to the correlation function whose characteristic width is a measu…
We generalize the theory of nuclear decay and capture of Gamow that is based on tunneling through the barrier and internal oscillations inside the nucleus. In our formalism an additional factor is obtained, which describes distribution of the wave function of the $α$ particle inside the nuclear region. We discover new most stable states (called quasibound states) of the compound nucleus (CN) formed during the capture of $α$ particle by the nucleus. With a simple example, we explain why these states cannot appear in traditional calculations of the $α$ capture cross sections based on monotonic p…
Event-by-event multiplicity fluctuations in central C+C, S+S, In+In, and Pb+Pb as well as p+p collisions at bombarding energies from 10 to 160 AGeV are studied within the HSD and UrQMD microscopic transport approaches. Our investigation is directly related to the future experimental program of the NA61 Collaboration at the SPS for a search of the QCD critical point. The dependence on energy and atomic mass number of the scaled variances for negative, positive, and all charged hadrons is presented and compared to the results of the model of independent sources. Furthermore, the nucleus-nucleus …
To systematically describe evaporation spectra for light and heavy compound nuclei over a large range of excitation energies, it was necessary to consider three ingredients in the statistical model. Firstly, transmission coefficients or barrier penetration factors for charged-particle emission are typically taken from global fits to elastic-scattering data. However, such transmission coefficients do not reproduce the barrier region of evaporation spectra and reproduction of the data requires a distributions of Coulomb barriers. This is possibly associated with large fluctuations in the compoun…
Interaction with a nucleus in pA collisions enhances the higher Fock components in the projectile proton. Effectively, this corresponds to an increase of the hard scale of the process by the saturation momentum Q^2 -> Q^2+Q_{sA}^2, which leads to an increased gluon distribution function at small x (but suppressed at x -> 1) compared to that in pp collisions. In the case of AA collisions the gluon distributions of bound nucleons in both nuclei turn out to be enhanced, i.e. to be boosted to higher saturation scales compared to pA collisions. A set of bootstrap equations relating the saturation s…
The idea that effective string tension increases as a result of the hard gluon kinks on a string is applied to study the strange particle production in proton-nucleus and nucleus-nucleus collisions. It is found that the effective string tension increases with the increase of centrality and mass of the colliding system as a consequence of the mini-(gluon)jet production stemming from the collective string-string interaction. This mechanism leads to strangeness enhancement in pA and AA collisions through the enhanced production of the strange quark pairs from the color field of strings. We discus…
The de-excitation of compound nuclei has been successfully described for several decades by means of statistical models. However, accurate predictions require some fine-tuning of the model parameters. This task can be simplified by studying several entrance channels, which populate different regions of the parameter space of the compound nucleus. Fusion reactions play an important role in this strategy because they minimise the uncertainty on the entrance channel by fixing mass, charge and excitation energy of the compound nucleus. If incomplete fusion is negligible, the only uncertainty on th…
During last 20 years there was revealed and published the phenomenon of the appearing of the time advance instead of the time delay at the region of a compound-nucleus resonance, distorted by the non-resonant background (in the center-of-mass (C-) system). This phenomenon is usually accompanied by a minimum in the cross section near the same energy. Here we analyze the cross section and the time delay of the nucleon-nucleus scattering in the laboratory (L-) system. In the L-system the delay-advance phenomenon does not appear. We use and concretize the non-standard analytical transformations of…
Representation in terms of a new parameter, exoticity, a measure of n-deficiency or p-richness, clearly brings out the saturation tendency of the product's maximum exoticity in a compound nuclear reaction as the compound nucleus is made more and more exotic using radioactive projectile (RIBs). The effect of this saturation on the production of new proton-rich species with RIBs over a wide Z-range has been discussed.
Entrance-channel potentials in nucleus-nucleus collisions, relevant for the synthesis of superheavy elements, are systematically studied within a semi-microscopic approach, where microscopic nuclear densities of the colliding spherical or deformed nuclei are used in semi-classical expressions of the energy-density functional. From experimental data on fusion windows evidence is found that the existence of pockets in the entrance-channel potentials is crucial for fusion. Criteria for the choice of best collision systems for the synthesis of superheavy elements are discussed.
Manifestations of P-,T-odd weak interaction between nucleons in nucleus are considered. Renormalization of this interaction due to residual strong interaction is studied. Mean squared matrix elements of P-,T-odd weak interaction between compound states are calculated. Correlators between P-,T-odd and P-odd, T-even weak interaction matrix elements between compound states are considered and estimates for these quantities are obtained.
The $J$-matrix inverse scattering approach can be used as an alternative to a conventional $R$-matrix in analyzing scattering phase shifts and extracting resonance energies and widths from experimental data. A great advantage of the $J$-matrix is that it provides eigenstates directly related to the ones obtained in the shell model in a given model space and with a given value of the oscillator spacing $\hbarΩ$. This relationship is of a particular interest in the cases when a many-body system does not have a resonant state or the resonance is broad and its energy can differ significantly from …
Statistical aspects of the dynamics of chaotic scattering in the classical model of $α$-cluster nuclei are studied. It is found that the dynamics governed by hyperbolic instabilities which results in an exponential decay of the survival probability evolves to a limiting energy distribution whose density develops the Boltzmann form. The angular distribution of the corresponding decay products shows symmetry with respect to $π/2$ angle. Time estimated for the compound nucleus formation ranges within the order of $10^{-21}$s.
Recent experimental results have revealed a surprisingly rich structure of multiparticle azimuthal correlations in high energy proton-nucleus collisions. Final state collective effects can be responsible for many of the observed effects, but it has recently been argued that a part of these correlations are present already in the wavefunctions of the colliding particles. We evaluate the momentum space 2-particle cumulant azimuthal anisotropy coefficients v_n{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. These would correspond to the fl…
The phenomenon of time resonances (or explosions) can explain the exponential reduction of the energy, which is accompanied for the certain degree by slight fluctuations under some conditions in the range of the energy strongly overlapped compound-resonances. These resonant explosions correspond to formation of several highly-exited non-exponentially decaying nuclear clots (partial compound nuclei consisting of several small groups of projectile nucleons and targets). This paper is a continuation and expansion of theoretical authors' work, which is a more general self-consistent version of the…
The set of parameters for alpha-nucleus potential is derived by using the data for both the alpha-decay half-lives and the fusion cross-sections around the barrier for reactions alpha+40Ca, alpha+59Co, alpha+208Pb. The alpha-decay half-lives are obtained in the framework of a cluster model using the WKB approximation. The evaluated alpha-decay half-lives and the fusion cross-sections agreed well with the data. Fusion reactions between alpha-particle and heavy nuclei can be used for both the formation of very heavy nuclei and spectroscopic studies of the formed compound nuclei.
Exploiting recently obtained analytic solutions of classical Yang-Mills equations for higher order perturbations in the field of the dilute object (proton), we derive the complete first saturation correction to the single inclusive semi-hard gluon production in high energy proton-nucleus collisions by applying the Lehmann-Symanzik-Zimmermann reduction formula. We thus finalize the program started by Balitsky (see Ref.~\cite{Balitsky:2004rr}) and independently by Chirilli, Kovchegov and Wertepny (see Ref.~\cite{Chirilli:2015tea}) albeit using a very different approach to carry out our calculati…
A theory of nucleus-nucleus collisions has been developed for kinetic energies substantially in excess of the binding energy. The very high pressure produced in the compound system as a result of the fusion of the two colliding nuclei is the reason for the subsequent hydrodynamic expansion of the nuclear medium. The energy and angular distributions of the reaction products are investigated. The charge distribution is also determined in the case where the nucleon and ion components of the reaction products are predominant. A solution is found for the expansion into vacuum of a sphere in which t…
The dependence of the transmission coefficient on the deformation, the collective rotation and excitation energy of the compound nucleus emitting light particles is introduced in the framework of Weißkopf's evaporation theory. The competition between fission and particle evaporation is treated by a~Langevin equation for the fission variable coupled to the emission process. Detailed calculations are presented on the decay of different Gd and Yb isotopes at an excitation energy of about 250~MeV. These calculations demonstrate the importance of the effects of nuclear deformation and of the initia…
The concept of compound nucleus was proposed by Niels Bohr in 1936 to explain narrow resonances observed in scattering of a slow neutron off atomic nuclei. A compound nucleus is a metastable state with a long lifetime, in which all the degrees of freedom are in a sort of thermal equilibrium. Fusion reactions are defined as reactions to form such compound nucleus by merging two atomic nuclei. Here a short description of heavy-ion fusion reactions at energies close the Coulomb barrier is presented. This includes: (i) an overview of a fusion process, (ii) a strong interplay between nuclear struct…
