Nucleon Stripping Research Articles

Nuclear reaction model for deuterons below 150 MeV/n in FLUKA

The lack of a dedicated model for nuclear reactions of deuterons at energies below 150 MeV/n has been a long-standing shortcoming of the general-purpose radiation-transport code FLUKA, preventing its use in applications either driven by deuteron beams or where reinteracting secondary deuterons play a significant role. A dedicated modelling effort has been undertaken to overcome this limitation. In this contribution, the essential ingredients of FLUKA’s novel model for low-energy deuteron nuclear inelastic interactions are briefly described, including nucleon stripping to the continuum, nucleon transfer to discrete states, and elastic break-up. The resulting model has been extensively benchmarked against experimental data prior to its inclusion in FLUKA v4-2.0.

Nucleon stripping in deuteron-induced spallation reactions at hundreds MeV/nucleon * *Supported by the National Natural Science Foundation of China under (11875328)

A nucleon-nucleus dynamics model was developed to investigate the proton-, neutron-, and deuteron-induced reactions at hundreds of MeV/nucleon. In this model, the trajectory of incident nucleon is described by classical mechanics, and the probability of reaction between the nucleon and nucleus is calculated by exponential damping. It is shown that the total reaction cross sections calculated by the model agree in general with the predictions by the CDCC and the experimental data. The model was applied to investigate the nucleon stripping in deuteron-induced reactions and its symmetry energy dependence.

Structure of the 1d2s Shell from the Data on Single-Nucleon-Transfer Reactions

For the stable silicon isotopes 28Si and 30Si, the energies and occupancies of single-particle states of the 1d2s shell are determined by analyzing the combined data for the nucleon stripping and pickup reactions. From the results of analysis and the available experimental data, the variation of the 1d2s proton-shell structure with increasing neutron number for the silicon isotopes with A = 26–34 is discussed.

Effect of nuclear-reaction mechanisms on the population of excited nuclear states and isomeric ratios

Experimental data on the cross sections for channels of fusion and transfer reactions induced by beams of radioactive halo nuclei and clustered and stable loosely bound nuclei were analyzed, and the results of this analysis were summarized. The interplay of the excitation of single-particle states in reaction-product nuclei and direct reaction channels was established for transfer reactions. Respective experiments were performed in stable (6Li) and radioactive (6Не) beams of the DRIBs accelerator complex at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, and in deuteron and 3Не beams of the U-120M cyclotron at the Nuclear Physics Institute, Academy Sciences of Czech Republic (Řež and Prague, Czech Republic). Data on subbarrier and near-barrier fusion reactions involving clustered and loosely bound light nuclei (6Li and 3He) can be described quite reliably within simple evaporation models with allowance for different reaction Q-values and couple channels. In reactions involving halo nuclei, their structure manifests itself most strongly in the region of energies below the Coulomb barrier. Neutron transfer occurs with a high probability in the interactions of all loosely bound nuclei with light and heavy stable nuclei at positive Q-values. The cross sections for such reactions and the respective isomeric ratios differ drastically for nucleon stripping and nucleon pickup mechanisms. This is due to the difference in the population probabilities for excited single-particle states.

On some approximations in the theory of halo nucleus reactions

The halo nucleus nucleon stripping reaction on a light target is studied using the diffraction theory of reactions with weakly bound nuclei. An improved version of the approximation of a small target’s radius (compared to the size of a halo nucleus) is formulated. Simple analytical expressions for the differential cross section and the longitudinal momentum distribution of observed particles that allow us to calculate them with good accuracy are obtained.

Cross Section Calculations of Deuteron-induced Reactions Using the Extended CCONE Code

We have extended the CCONE code to make it possible to calculate cross sections for deuteron-induced reactions. Elastic breakup and stripping reactions to continuum are calculated using another codes based on the Continuum-Discretized Coupled-Channels theory (CDCC) and the Glauber model, respectively, and the calculated results are inputted to the CCONE code as direct reaction components. Statistical decay from compound nuclei formed by nucleon stripping and deuteron absorption is calculated with the exciton and Hauser-Feshbach models implemented in the original CCONE code. The extended CCONE code is applied to analyses of deuteron-induced reactions on 27Al and 58Ni. CDCC calculations for deuteron elastic scattering show good agreement with the experimental data at incident energies of several tens of MeV. The calculated double-differential (d,xp) cross sections reproduce the measured ones at forward angles for incident energies of 56 and 100 MeV fairly well.

Relations between the differential cross sections for diffractive processes of nucleon stripping and halo-nucleus core stripping

A comparative analysis of the nucleon stripping and core stripping reactions induced by a halo nucleus is presented on the basis of certain models for diffractive processes. It follows from calculations for the halo nucleus 11Be that the transverse momentum distribution of nucleons for core stripping (as the longitudinal momentum distribution) is less distorted by absorption in a target than the distribution of core fragments for nucleon stripping. The obtained relations between the cross sections for the stripping reactions simplify interpretation of the calculation results.

Absorption effects in halo-nucleus core or nucleon stripping reactions

Inclusive halo-nucleus core or nucleon stripping reactions are considered on the basis of a potential three-body model using the eikonal and adiabatic approximations. Clear analytical expressions for the cross sections of these reactions are obtained, and numerical calculations for 11Be halo nucleus are performed. Constituent absorption by the target nucleus substantially influences the integral and differential (with respect to longitudinal momentum) nucleon stripping cross section. It is demonstrated that the differential core stripping cross section contains more complete information on the unperturbed wave function of the halo nucleus.

Neutron shell structure of 58,60,62,64Ni nuclei and its study within a mean-field model with dispersive optical-model potential

Experimental single-particle energies and occupation probabilities for neutron states near the Fermi energy in 58,60,62,64Ni nuclei were obtained from joint evaluation of the data on nucleon stripping and pickup reactions on the same nucleus. Degeneracy of the 2p 3/2,1/2 and 1f 5/2 subshells was demonstrated. The resulting data were analyzed within a mean-field model with dispersive optical-model potential. Good agreement was obtained between the calculated and experimental single-particle energies of the subshells.

Assessment of deuteron-induced reaction mechanisms at low and medium energies

An extended analysis of the nuclear reaction mechanisms involved in the deuterons interaction with 63,65 Cu is presented. First, the available elastic-scattering data analysis provide d us the optical potential for reac- tion cross sections calculations. An increased effort has been devoted to the breakup mechanism, both the elastic breakup and the breakup fusion contributions to the different activation cross sections being carefully considered. Next, the direct reaction contributions through the one nucleon stripping re action cross sections have been cal- culated. Finally, the pre-equilibrium and compound-nucleus cross-section calculation, corrected for the breakup and stripping decrease of the total reaction cross section, completed the d euteron activation cross-section anal- ysis. The overall agreement between the measured and calculated deuteron activation cross sections proves the correctness of the nuclear mechanisms account.

Analysis of deuteron breakup reactions for energies up to 100 MeV

Inclusive nucleon spectra from deuteron breakup reactions on 7Li and 12C up to 100 MeV are analyzed by using the continuum discretized coupled channels theory for elastic breakup process and the Glauber model for nucleon stripping process. The preequilibrium and evaporation components are estimated phenomenologically in terms of the moving source model. The calculation reproduces a prominent bump observed around half the incident energy in experimental inclusive spectra at forward angles quite well. The present analysis clarifies that the stripping process is more dominant than the elastic breakup process in deuteron breakup reactions on 7Li and 12C.

Analysis of deuteron breakup reactions onLi7for energies up to 100 MeV

Inclusive nucleon spectra from deuteron breakup reactions on $^{7}\mathrm{Li}$ are analyzed in terms of the continuum discretized coupled channels theory for the elastic breakup process and the Glauber model for the nucleon stripping process. Both theoretical models use the same phenomenological nucleon optical potential of $^{7}\mathrm{Li}$ and have no other free parameters. The calculations reproduce well a prominent bump observed around half the incident energy in experimental inclusive spectra of 40-MeV ($d,\mathit{xn}$) and 100-MeV ($d,\mathit{xp}$) reactions at forward angles. The analysis shows that the stripping process is more important than the elastic breakup process in deuteron breakup reactions on $^{7}\mathrm{Li}$.

Direct surface transfer reactions induced by a 1102MeV40Ar beam onZn68target nucleus

Few nucleon pickup and stripping reactions have been analyzed in terms of direct surface transfer reactions leading to continuum states. Excellent agreements were obtained with the prediction of the diffractional model.

Excitation of high-spin particle-hole states in A = 28 nuclei by 27Al(α, t) and (α, 3He) reactions

Abstract The 27 Al(α, t) and (α, 3 He) reactions have been measured at E α = 64.5 MeV. The experimental angular distributions were analyzed by the exact finite-range DWBA calculations assuming a nucleon stripping mechanism. The distributions of spectroscopic strengths for the single-particle transitions with transferred angular momenta l = 0, 1, 2, 3 and 4 have been obtained. The strengths for the transitions to the stretched 6 − states in 28 Si and 28 Al are compared to those obtained from inelastic scattering on 28 Si. The present results show no distinctive differences in the structures for 6 − T = 0 and 1 states in 28 Si such as are observed in proton and pion inelastic scattering on 28 Si.

Inelastic interactions of 9.38 GeV/c deuteron in emulsion

Characteristics of the inelastic interactions of 9.38 GeV/c deuterons with nuclear emulsion nuclei have been studied. These have been compared with nucleon-nucleus interactions at a corresponding momentum. The probability of nucleon stripping in deuteron-nucleus interactions has been observed to be 0.5. The charged particle multiplicity in deuteron-nucleus interactions exhibitA-dependence of the typeAα with α=0.08. The experimental data disagree with KNO scaling.

Heavy-ion charge exchange reactionSi28(O18,F18)Al28

The angular distribution has been measured for the 3/sup +/ and 2/sup +/ ground state doublet in /sup 28/Al with the heavy-ion charge exchange reaction /sup 28/Si(/sup 18/O,/sup 18/F)/sup 28/Al at the incident beam energy of 56 MeV. It has been analyzed in terms of the microscopic one-step direct charge exchange model and the second-order DWBA approach with recoil effect taking into account the two-step successive transfer: one nucleon stripping and pickup, and pickup and stripping process. The general shape of angular distribution has been reproduced by both approaches. The strength of the spin-isospin dependent two-body interaction potential extracted from one-step calculations is close to the upper limit of uncertainties reported in the light-ion charge exchange experiment. The two-step mechanism turns out to be also important and could be a competing process.

Two-nucleon transfer: Random-phase approximation theory, pairing vibrations, and the extended basis shell model

Previous calculations have shown that the accurate prediction of two-nucleon overlap factors requires the inclusion of very large numbers of highly excited configurations. These "extended basis shell model" calculations treat a pair of nucleons added to an inert core. In the present paper, the two-particle random-phase approximation theory of Vary and Ginocchio is used to generalize the extended basis shell model to include the effect of core correlations. Including them is shown to have a small effect on two-nucleon stripping reactions, such as $^{16}\mathrm{O}(t, p)^{18}\mathrm{O}$. However, the random-phase approximation enables us to include the effect of the highly excited single-particle states on the transition amplitudes for the pickup of a pair, e.g., $^{16}\mathrm{O}(p, t)^{14}\mathrm{O}$. Because the admixed states have wave functions which are large in the surface and exterior regions, they result in large enhancements of pickup cross sections. We have also studied the breakdown of the random-phase approximation, when eigenvalues become complex. We provide a proof, for an arbitrary two-body interaction, that the potential strength for which the random-phase approximation eigenvalues become complex, is the minimum strength for which nontrivial solutions to the Hartree-Fock-Bogolyubov equations exist.NUCLEAR REACTIONS Core correlations included in EBSM calculations of two nucleon stripping reactions using particle-RPA; influence of EBSM on two nucleon pickup reactions; breakdown of RPA.

A study of the (α, t) reaction on 19F, 27Al, 51V and 59Co

The angular distributions of tritons from the (α, t) reaction on 19F, 27Al, 51V and 59Co nuclei corresponding to the (0 +) ground states and (2 +) excited states in the final nuclei have been measured in the angular range between 15° and 170° at α-particle energies of 25 MeV. For reactions on 27Al and 51V nuclei, the differential excitation functions have also been obtained at different angles of outgoing tritons at E α from 20 to 25 MeV. The experimental angular distributions are analysed by the DWBA approximation on the assumption of a nucleon stripping mechanism. The analyses of the present results and the data obtained earlier for the ( α, t) reaction on the 1 p shell nuclei, A ≲ 30, reveal that the distinguishing feature of the reaction under study is the presence of backward angle peaks in the reaction cross section, which appear to be associated with exchange processes. For the ( α, t) reaction on the heavier nuclei ( A > 30), the dominant mechanism is nucleon stripping.

Effective two-body forces in light and medium mass nuclei

From the spectroscopic information provided by single particle stripping reactions, we have extracted average effective two-body interaction between nucleons in thep-, sd-, andfp- shells. Using the derived interaction parameters, we have calculated the energy centroids of the level spectra of residual nuclei obtained via single nucleon stripping reactions involving light and medium mass nuclei as targets.

Réactions de transfert de plusieurs nucléons entre ions lourds

Population of n-particles- n-hole states is studied in three, four and five nucleon stripping reactions by heavy ions, leading to the 16O residual nucleus. High-energy excitation levels of 16O are obtained up to 26 MeV. All of these reactions are very selective, especially alpha transfer reactions. Several 2p-2h and 4p-4h states are populated by three and five nucleons transfer reactions. Angular distributions measured at forward angles (≧ 1.5° lab) exhibit a typically diffractional pattern suggesting that a direct interaction mechanism is predominant.