Total Reaction Cross Sections Research Articles

Incomplete absorption reactions at high energy

Abstract The total reaction cross section of high-energy nucleus–nucleus collision reflects the nuclear density profiles of the colliding nuclei and is a standard tool to investigate the size properties of short-lived unstable nuclei. This 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 the overlap density of two colliding nuclei is low enough. In this paper, we propose a way to quantify this incompleteness, i.e., the “blackness” of the total reaction cross section. The significance of this quantification is shown by taking an example of the total reaction cross sections of proton-rich C isotopes.

Coherent description of elastic scattering and fusion at near-barrier energies for the Be9+Pb208 and Be9+Au197 reactions

Elastic scattering, total reaction, and fusion cross sections of the systems $^{9}\mathrm{Be}+^{208}\mathrm{Pb}$ and $^{9}\mathrm{Be}+^{197}\mathrm{Au}$ at near-barrier energies, are coherently analyzed into two theoretical contexts. In a phenomenological approach, a BDM3Y1 interaction is used in an optical model potential analysis of the elastic-scattering data and the energy dependence of the potential is mapped around the Coulomb barrier. In a second approach, the elastic scattering is investigated within a four body framework by using the continuum-discretized coupled-channels method. In both scenarios, total reaction cross sections are determined and compared with phenomenological predictions. Moreover, an effective potential is obtained and in a one barrier penetration model analysis, the fusion excitation function is determined and compared with experimental data, further validating our analysis.

Measurement of the Ne18(α,p)Na21 reaction with the ANASEN active-target detector system at Ec.m.=2.5–4 MeV

The $^{18}\mathrm{Ne}(\ensuremath{\alpha},p)^{21}\mathrm{Na}$ reaction plays a significant role in Type-I X-ray bursts. It is a major path in the breakout from the hot-CNO cycles to the synthesis of heavier elements in the $\ensuremath{\alpha}p$- and $rp$-processes. An experiment to determine the cross section of this reaction was performed with the ANASEN active-target detector system, determining the cross section at energies between 2.5 and 4 MeV in the center-of-mass frame. The measured cross sections for reactions populating the ground state in $^{21}\mathrm{Na}$ are consistent with results obtained from the time-inverse reaction, but significantly lower than the previously published experimental data of direct measurements. The total cross sections are also compared with those derived from indirect methods and statistical-model calculations. This experiment establishes a new experimental data set on the excitation function of the $^{18}\mathrm{Ne}(\ensuremath{\alpha},p)^{21}\mathrm{Na}$ reaction, revealing the significance of the excited states' contributions to the total reaction cross section and allowing us to separate the contribution of the $(\ensuremath{\alpha},2p)$ reaction. The impact of the measured cross section on thermal reaction rates is discussed.

Excited Electronic State Cross Sections for Group 3 Halide and Oxide Production: Evaluating Relative Excited-State Quantum Yields

The cross sections for excited-state formation from the reactions of the group 3 metals, Sc, Y, and La, with F2 and NO2, are evaluated from experimental data. Detailed calibrations indicate that the cross sections for MF formation greatly exceed those for MO formation. The experimentally determined cross sections are compared to upper bounds for total reactive cross sections. Based on this comparison, the ratios of excited state to ground state product formation (quantum yield) are evaluated. The reactions of Sc and Y with F2, which produce excited states selectively, may represent candidates to create a population inversion for use in a chemical laser.

A Theoretical Kinetic and Classical Dynamic Investigation of CN + OH and CN + OD Reactions on an Interpolated Potential Energy Surface

In the current work, kinetic and dynamic parameters in reactive and non-reactive collisions between CN and OH radicals were investigated upon an interpolated potential energy surface using MP2/6-311G++(d,p) ab-initio method. The total and individual reaction probability and cross-section, for all reactions, were obtained and applied to calculate the rate constant and rate expression. In non-reactive trajectories, the effect of the impact parameter and relative translational energy of particles on the deflection angle was also investigated. To investigate the kinetic isotopic effect, the deuterium was used instead of hydrogen atom to illustrate the effect of mass of attacking radical and target molecule on physical observable such as reaction probability and cross-section

Large enhancement of total reaction cross sections at the edge of the island of inversion in Ti, Cr, and Fe isotopes

A systematic analysis of nuclear deformation is made for neutron-rich Ti, Cr, and Fe isotopes to explore the nuclear structure in the island of inversion near N = 40, where strong nuclear deformation is predicted. The nuclear ground states are obtained by the Skyrme Hartree-Fock method in three-dimensional coordinate space, which properly describes any nuclear shape. Three types of Skyrme interactions are employed to generate various deformed states in its isotopic chain. We find that in the island of inversion the occupation of highly elongated intruder orbits induces not only large quadrupole deformation but also large hexadecapole deformation. This appears as a sizable enhancement of the nuclear matter radius, showing the characteristic shell effect of the density profile near the nuclear surface. We show that the edge of the island of inversion, where the intruder orbit starts being occupied, can be determined by measuring the enhancement of the total reaction cross section at high incident energy. The possibility of constraining the hexadecapole deformation by a measurement of the total reaction cross sections is discussed.

Self-consistent description of the halo nature of 31Ne with continuum and pairing correlations

Background: A relativistic structure model has previously been used to predict a halo structure for 31Ne (Zhang et al 2014 Phys. Lett. B 730 30), consistent with halo signatures from measured reaction cross sections of Ne isotopes bombarding Carbon targets. However, previous attempts to calculate those cross sections with reaction models were missing contributions from resonances and pairing correlations in their structure input. Purpose: Use a reaction model with our relativistic fully microscopic structure model input to predict these cross sections and momentum distributions and analyze for possible halo signatures. Methods: Structure input for exotic Ne isotopes were obtained via the analytical continuation of the coupling constant (ACCC) method based on the relativistic mean field (RMF) theory with Bardeen–Cooper–Schrieffer (BCS) pairing approximation, the RAB approach. Total reaction cross sections, one-neutron removal cross sections, and momentum distributions of breakup reaction products were calculated with a Glauber model using our relativistic structure input. Results: Our predictions of total reaction and one-neutron removal cross sections of 31Ne on a Carbon target were significantly enhanced compared with those of neighboring Neon isotopes, agreeing with measurements at 240 MeV/nucleon and consistent with a single neutron halo. Furthermore, our calculations of the inclusive longitudinal momentum distribution of the 30Ne and valence neutron residues from the 31Ne breakup reaction indicate a dilute density distribution in coordinate space, another halo signature. Conclusions: We give a full description of the halo nature of 31Ne that includes a self-consistent use of pairing and continuum contributions that makes predictions consistent with reaction cross section measurements. This approach can be utilized to determine the halo structure of other exotic nuclei.

Measurement of the 7Be(p, γ)8B reaction cross section with the recoil mass separator ERNA

The cross section of 7Be(p,γ)8B represents one of the most important nuclear inputs for the prediction of the high energy component of solar neutrinos and it has also a direct impact on the 7Li abundance after the Big Bang Nucleosynthesis. The importance of this reaction triggered an intense experimental work over the last decades, where discrepancies were observed between the results of different measurements. In addition, a question remains about possible common systematic effects, considering that all measurements share the same experimental approach, i.e. an intense proton beam impinging on a 7Be radioactive target. Inverse kinematics, i.e. a 7Be ion beam and a hydrogen target, with the direct measurement of the total reaction cross section by means of the detection of the 8B recoils, can shed light on such systematic effects. Efforts attempted so far were limited by the low 7Be beam intensity. We present here the results of a new measurement at Ecm = 376 to 819 keV using a high intensity 7Be beam in combination with a windowless gas target and the recoil mass separator ERNA (European Recoil mass separator for Nuclear Astrophysics) at CIRCE (Center for Isotopic Research on Cultural and Environmental heritage), Caserta, Italy. Our results, including the systematic error, are compatible with previous measurements that yields lower value of S17(0) and are compatible with the currently accepted value from [1] only at a 2-σ level.

Oxygen Formation in the Light of Gamma-Beams: [Precision Measurements of the 12C(α, γ) Reaction with Gamma-Beams and a Time Projection Chamber

The carbon/oxygen (C/O) ratio at the end of stellar helium burning is not known with sufficient accuracy due to the large uncertainty in the cross-section of the 12C(α, γ)16O reaction. We developed a new method to measure this reaction that is significantly different from the experimental efforts of the past four decades. Data were measured with vanishingly small background, inside one detector, that also serves as an active target (AT-TPC). Angular distributions of the 12C(α, γ)16O reaction were obtained by measuring the inverse 16O(γ, α)12C reaction with gamma-beams (from the HIγS facility) and an optical readout time projection chamber (O-TPC) detector. We agree with current world data on the measured total reaction cross-section. We further evidence the strength of our method with angular distributions measured over the 1–resonance at Ecm ~ 2.4 MeV. We extract the E1-E2 mixing phase angle (ϕ12) over this resonance and obtained values that follow the trend of prediction based on unitarity of the scattering amplitude. Our technique promises to yield results that will surpass the quality of the currently available data. We continue these measurements to lower energies at the HIγS facility of TUNL at Duke University, and anticipate measurements down to Ecm = 1.1 MeV at the ELI-NP, the EU facility in Romania..

Simultaneous analysis of elastic scattering and fusion in He6+Zn64 : A transition in direct reaction mechanisms, striking threshold anomalies, and halo effects

Using the extended optical model, a simultaneous analysis is carried out of elastic scattering and fusion reactions induced by the neutron halo $^{6}\mathrm{He}$ projectile on a $^{64}\mathrm{Zn}$ target. Dynamic polarization potentials ${U}_{F}$, ${U}_{D}$ are introduced which can be associated to fusion and direct couplings, respectively. Appropriate fitting parameters leading to dispersive potentials are found which provide a good simultaneous description of the data. An unexpected local maximum is uncovered in the energy dependence of the total reaction cross sections, indicating a transition in the involved direct reaction processes, and a possible underlying mechanism is discussed. ${U}_{F}$ is found to follow the normal threshold anomaly but with an unusually large threshold energy. ${U}_{D}$, on the other hand, exhibits a breakup threshold anomaly, but with a strikingly high value of the peak energy, which can be associated to the above-mentioned transition. The results also are discussed within the context of possible halo effects.

Vibrational and Rotational Gaussian Binning selections on QCT calculations for the OH + D2 → HOD((vHO’, vHOD’, vOD’), J’) + D reaction

Abstract A large sample has been employed to obtain total reaction cross sections and product state distributions (translational, vibrational and rotational) for the title reaction. Quasi-Classical Trajectory (QCT) calculations and the Gaussian Binning (GB) methodology have been used on Wu-Schatz-Lendvay-Fang-Harding (WSLFH) and Neural Networks (NN) potential energy surfaces. After a first selection, Vibrational-Gaussian Binning (V-GB), (vHO’, vHOD’, vOD’), and a second selection, Rotational-Gaussian Binning (R-GB), although the preference observed (odd or even J') is not exactly followed by each vibrational excitation of HOD, there is a similar behavior to the physical laser phenomenon observed in another triatomic molecule utilized in the gas laser of CO2. The dynamics of polyatomic chemical reactions (e.g., OH + D2 → HOD* + D and its isotopic variants), of relevance in the excitation/emission processes of current and future chemical lasers, could be studied theoretically from the results obtained in this article.

Precision measurements on oxygen formation in stellar helium burning with gamma-ray beams and a Time Projection Chamber

The carbon/oxygen (C/O) ratio at the end of stellar helium burning is the single most important nuclear input to stellar evolution theory. However, it is not known with sufficient accuracy, due to large uncertainties in the cross-section for the fusion of helium with 12C to form 16O, denoted as 12C(α, γ)16O. Here we present results based on a method that is significantly different from the experimental efforts of the past four decades. With data measured inside one detector and with vanishingly small background, angular distributions of the 12C(α, γ)16O reaction were obtained by measuring the inverse 16O(γ, α)12C reaction with gamma-beams and a Time Projection Chamber (TPC) detector. We agree with current world data for the total reaction cross-section and further evidence the strength of our method with accurate angular distributions measured over the 1− resonance at Ecm ~ 2.4 MeV. Our technique promises to yield results that will surpass the quality of the currently available data.

Analysis of elastic and inelastic scattering of Ne20 on Ge76 at 306 MeV

Angular distributions of the differential cross section for $^{20}\mathrm{Ne}+^{76}\mathrm{Ge}$ elastic and inelastic scattering at energy 306 MeV are analyzed in the framework of the optical model. The analysis is performed using the coupled-channels mechanism by taking into account the effect of the low-lying states, ${0}^{+}$ and ${2}^{+}$ for the projectile $^{20}\mathrm{Ne}$ $({E}_{\mathrm{ex}.}=1.634 \mathrm{MeV})$, target $^{76}\mathrm{Ge}$ $({E}_{\mathrm{ex}.}=0.563 \mathrm{MeV})$ nuclei, and their mutual excitation $({2}^{+},{2}^{+})$. Results are obtained with the conventional phenomenological Woods-Saxon potential and three different semimicroscopic potentials using the double folding model. Two real cluster potential models are calculated based upon the cluster structure of $^{20}\mathrm{Ne}$ nucleus as 5\ensuremath{\alpha} and $\ensuremath{\alpha}+^{16}\mathrm{O}$. For the sake of comparison, the real of the density-energy-dependent CDM3Y6 potential is considered. The imaginary part for the three real potentials is treated in a standard Woods-Saxon form. The calculations show that the experimental data can be reproduced successfully with a scale factor close to 1. The coupled channels have a weak effect on the elastic scattering with significant differences in calculations of the volume integrals and the total reaction cross sections compared to the available previous study for this reaction. Other future studies are, therefore, required.

Comparison of validation methods of simulations for final state interactions in hadron production experiments

Neutrino cross section and oscillation measurements depend critically on modeling of hadronic final state interactions (FSI). Often, this is one of the largest components of uncertainty in a measurement. This is because of the difficulty in modeling strong interactions in nuclei in a consistent quantum-mechanical framework. FSI models are most often validated using hadron-nucleus data which introduces further uncertainties. The alternative is to use transparency data where the hadron starts propagating from inside the nucleus and the probability of interaction is measured as a function of hadron energy. This work examines the relationship between the $\pi^+$ and proton total reaction cross section and transparency from a simulation viewpoint.

Description of elastic scattering induced by the unstable nuclei 9,10,11,13,14C * *Supported by the National Natural Science Foundation of China (11405099, 11575291, 12065003), Scientific and Technological Innovation Programs of Higher Education Institutions (STIP) in Shanxi of China (2019L0743) and Science Foundation for General in Shanxi of China (201901D111317). This work is also supported by the Open Project of Guangxi Key

The elastic-scattering angular distributions and total reaction cross sections of projectiles were predicted using the obtained and global optical model potentials, respectively. The predictions were analyzed in detail by comparison with the available experimental data. The results indicate that the and global optical model potentials provide a satisfactory description of the elastic scattering data for the reactions induced by the . For the neutron-rich carbon isotope , the elastic scattering can be well described by changing the real part radius parameter of the global optical model potential. Possible physical explanations for the observed differences are further discussed.

An investigation of radiative proton–capture reactions in the Cd–In mass region

The reaction network in the neutron–deficient part of the nuclear chart around A∼100 contains several nuclei of importance to astrophysical processes, such as the p–process. This work reports on the results from recent experimental studies of the radiative proton-capture reactions 112,114Cd(p,γ)113,115In. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched 112Cd and 114Cd targets. Two different techniques, the in–beam γ–ray spectroscopy and the activation method have been employed, with the latter considered necessary to account for the presence of low–lying isomers in 113In (Eγ≈392 keV, t1/2≈100 min), and 115In (Eγ≈336 keV, t1/2≈4.5 h). Following the measurement of the total reaction cross sections, the astrophysical S factors have been additionally deduced. The experimental results are compared with Hauser–Feshbach theoretical calculations carried out with the most recent version of TALYS. The results are discussed in terms of their significance to the various parameters entering the models.

Probing proton halo effects in the 8B+64Zn collision around the Coulomb barrier

Proton halo effects in the 8B+64Zn reaction at an energy around 1.5 times the Coulomb barrier have been studied at HIE-ISOLDE CERN using, for the first time, the only existing postaccelerated 8B beam. This, together with the use of a high granularity and large solid angle detection system, allowed for a careful mapping of the elastic angular distribution, especially in the Coulomb-nuclear interference region. Contrary to what is observed for the one-neutron halo nucleus 11Be on the same target in a similar energy range, the analysis of the elastic scattering angular distribution shows only a modest suppression of the Coulomb-nuclear interference peak, with no remarkable enhancement of the total reaction cross-section. Inclusive angular and energy distributions of 7Be produced in direct reaction processes have also been measured. The comparison of these data with the results of theoretical calculations for the elastic and non-elastic breakup contributions indicate that both processes are important. Overall, the experimental data suggest a 8B collision dynamics at the barrier very different from the one of neutron halo nuclei, showing only modest effects of coupling to continuum. This behaviour can be interpreted as due to the presence of the additional Coulomb interactions halo-core and halo-target together with the presence of the centrifugal barrier felt by the valence proton of 8B.

Fragmentation of carbon on elemental targets at 290AMeV

The total charge-changing cross-sections and the partial cross-sections for projectile fragments (PFs) production for the fragmentation of 12C on C, Al, Cu, Pb and CH2 targets at the highest energy of 290[Formula: see text]A[Formula: see text]MeV were studied. It was found that the total charge-changing reaction cross-sections and the partial reaction cross-sections of PFs production were independent of the beam energy, and increased with increase of mass of target for the same beam energy. The total charge-changing reaction cross-section was the same as the prediction of Bradt–Peters semi-empirical formula, PHITS and NUCFRG2 simulation models. The partial cross-section of PFs production increased with the increase of the mass of target, and it was the same as the prediction of NUCFRG2 models. The mean scattering angle of projectile particle was smaller than the average emission angle of PF, and the width of scattering angle distribution of projectile particle was smaller than that of emission angle distribution of PFs. The mean emission angle of PFs does not obviously depend on the target mass and beam energy in our studied beam energy regions.

The effects of finite range of the NN force and in-medium NN cross-section on the proton–nucleus total reaction cross-section

The effects of the finite range of the NN force and medium modifications on the nucleon-nucleus total reaction cross sections are investigated in the framework of the Coulomb modified Glauber model (CMGM). Different models of the nuclear densities are used. Comparison with experiments is considered. It is found that the effects of finite range strongly increase the reaction cross section at low and intermediate energies. Medium modifications of the NN cross section reduced the reaction cross section at low and intermediate energies. Both effects are found to be important for a better description of the proton- and neutron-nucleus total reaction cross sections.

Production Cross Sections and Induced Activity in Ge Isotopes by 30 MeV Proton Beam

The excitation functions of 70 Ge(p,n) 70 As, 72 Ge(p,n) 72 As, 74 Ge(p,n) 74 As and 76 Ge(p,n) 76 As reactions were studied from reaction threshold to 30 MeV by using EMPIRE-3.2 and TALYS-1.9 nuclear reaction model codes. This study is important because some isotopes produced are important for positron emission tomography (PET). Direct, pre-compound and compound nuclear reactions are considered as main nuclear reaction mechanisms in the codes. The calculated excitation functions have been compared with available experimental data and found to be in fair agreement. Furthermore, the contributions of various reaction mechanisms have been studied in total reaction cross-section that varies with the incident proton energy. The estimation of induced radio activity in thick Ge target due to the primary interaction is carried out for1μA, 30 MeV proton beam.