Single-nucleon Transfer Reactions Research Articles

Study of single-nucleon transfer reactions in the 18O+48Ti collision at 275 MeV

The study of single-nucleon transfer reactions for the 18O+48Ti system was pursued at the energy of 275 MeV as part of a more systematic study which is undertaken within the NUMEN and NURE experimental campaigns. The aim is to measure the complete set of available reaction network which are characterized by the same initial and final-state wavefunctions as the more suppressed double charge exchange reactions. Understanding the degree of competition between successive nucleon transfer and double charge exchange reactions is crucial for the description of the meson-exchange mechanism. In this respect, angular distribution measurements for one- and twonucleon transfer reactions for the 18O+48Ti system were carried out at theMAGNEX facility of INFN-LNS in Catania. An overview of the data analysis for the 48Ti(18O,19F)47Sc and 48Ti(18O,17O)49Ti reactions will be presented.

Multichannel experimental and theoretical approach to the C12(O18,F18)B12 single-charge-exchange reaction at 275 MeV: Initial-state interaction and single-particle properties of nuclear wave functions

Background: Single-charge-exchange reactions are appropriate tools to study the nuclear response to one-particle/one-hole isospin probes, gaining additional interest from the connection to beta decay. This analogy has been recently extended to second order, connecting double-charge-exchange reactions and double beta decays. Nowadays, the availability of powerful experimental setups and advanced nuclear theories and models allows one to access precious information on key nuclear structure aspects embedded in the widely sought neutrinoless double beta decay. Purpose: We intend to bring to light the main nuclear structure and reaction features involved in the O18+C12 collision at 275 MeV incident energy. In this paper, the main focus is on the role of the initial- and final-state interactions in the overall reaction dynamics and on the single-particle nuclear structure properties accessed via the study of single-nucleon transfer reactions. Forthcoming articles will be devoted to go into the details of the response to one- and two-particle/hole isospin probes. Methods: Cross-section energy spectra and angular distributions were measured in a unique experimental setup for the C12(O18,O18)C12 elastic and inelastic scattering, the C12(O18,O17)C13 one-neutron stripping, the C12(O18,F19)B11 one-proton pickup, and the C12(O18,F18)B12 single-charge-exchange nuclear reactions. A unique comprehensive and coherent theoretical calculation, able to describe the whole network of direct reactions using state-of-the-art nuclear structure and reaction theories, was performed, and it is presented for the first time in this article. This holistic approach, applied both to the experimental and theoretical analysis, is the main feature and worth of the work here presented. Results: The energy and angular resolutions achieved in each reaction channel allowed us to isolate specific transitions and to map the diffraction patterns in the angular distributions. The cross-section calculations describe well the experimental data, both in terms of the absolute values and diffraction patterns. Although the distorted wave Born approximation (DWBA) calculations prove to be accurate in describing all the studied channels, better results are achieved when the couplings to inelastic transitions in both the incoming and outgoing partitions are introduced, as done in the coupled channels Born approximation (CCBA) calculations. Otherwise, no real improvement is found when the coupling effects among different partitions are explicitly taken into account in the coupled reaction channels (CRC) calculations. Conclusions: The multichannel approach proposed in this paper is a promising method for accurate investigations of direct reactions originating in heavy-ion collisions. This is quite appealing for the precise spectroscopy of heavy nuclei proposed in many areas of nuclear physics. An example is the NUMEN project with its challenging commitment to provide valuable information on neutrinoless double beta decay nuclear matrix elements from single- and double-charge-exchange cross-section measurements.1 MoreReceived 18 July 2022Accepted 23 January 2023DOI:https://doi.org/10.1103/PhysRevC.107.024605©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCharge-exchange reactionsCollective modelsDirect reactionsNuclear many-body theoryOptical, coupled-channel & distorted wave modelsShell modelSpectroscopic factors & electromagnetic momentsTransfer reactionsProperties6 ≤ A ≤ 19TechniquesNuclear data analysis & compilationNuclear reactionsSpectrometers & spectroscopic techniquesNuclear Physics

O18 -induced single-nucleon transfer reactions on Ca40 at 15.3A MeV within a multichannel analysis

Background: Nucleon transfer reactions are selective tools for nuclear physics investigations. The theoretical and computational limits affecting in the past their data analysis could be nowadays surmounted thanks to the advent of methods with refined approximations and constraints, even when heavy-ion collisions are considered. Purpose: Modern microscopic calculations of heavy-ion-induced transfer reactions combined with precise experimental data offer the chance for accurately testing different reaction models as well as the nuclear structure description of the involved nuclear states. Method: Single proton and neutron transfer reactions were measured with the MAGNEX magnetic spectrometer for the O18+Ca40 system at 15.3A MeV. Excitation energy spectra and angular differential cross section distributions were extracted. The experimental results are compared with theoretical calculations performed in distorted wave and coupled channel Born approximation. The use of a coupled channel equivalent polarization potential to effectively describe the coupling effects affecting the initial state interaction is also considered. Spectroscopic amplitudes derived from a large-scale shell model with appropriate interactions adapted for the involved nuclei are employed. Results: Our theoretical calculations are in good agreement with experimental data, without the need for any scaling factor, validating the adopted reaction and nuclear structure parameters. Moreover, under the present experimental conditions, a weak dependence of the obtained results on the choice of the reaction models was observed. Conclusions: The good agreement between experimental and theoretical results validates the reliability of the parameter sets entering the calculations. They are extracted from or tested in complementary analyses of other reaction channels under the same experimental conditions. Such a multichannel approach represents the best option to pursue a solid, comprehensive, and model-independent description of the single-nucleon transfer reactions. The successful description of the present one-nucleon transfer data is also propaedeutic to the accurate assessment, under the same theoretical description, of higher-order transfer processes, like the sequential nucleon transfer mechanisms which are in competition with the direct charge exchange reactions.Received 14 September 2021Accepted 16 November 2021DOI:https://doi.org/10.1103/PhysRevC.104.064609©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLow & intermediate energy heavy-ion reactionsModels & methods for nuclear reactionsTransfer reactionsTechniquesOptical, coupled-channel & distorted wave modelsNuclear Physics

A Brief Review on the Development of Theories of Deuteron Stripping Reactions

As one type of single nucleon transfer reactions, deuteron stripping reaction has been playing an important role in the study of the single particle structure of atomic nuclei. Also, as a typical three-body nuclear reaction, deuteron stripping reaction is also an important subject in the development of direct nuclear reaction theories. We briefly review the history of the study of deuteron stripping reactions, focusing on the evolution of its theoretical descriptions, and the differences and the relations of the Plane Wave Born Approximation(PWBA), the distorted wave Born approximation(DWBA), the Continuum Discretized Coupled Channel method(CDCC), the Adiabatic Wave Approximation(ADWA), and the approach based on the Faddeev equations. Some important problems being currently addressed in deuteron stripping reaction theories and those should be addressed in near future are also discussed, including deuteron strippings at intermediate and high energies, theory for transfer to continuum states of the residue nuclei, applications of dispersive optical model potentials and non-local potentials, etc. Some preliminary results of our theoretical calculations for deuteron stripping at intermediate and high energies are presented.

One-proton transfer reaction for the O18+Ti48 system at 275 MeV

Single-nucleon transfer reactions are processes that selectively probe single-particle components of the populated many-body nuclear states. In this context, recent efforts have been made to build a unified description of the rich nuclear spectroscopy accessible in heavy-ion collisions. An example of this multichannel approach is the study of the competition between successive nucleon transfer and charge exchange reactions, the latter being of particular interest in the context of single and double beta decay studies. To this extent, the one-proton pickup reaction Ti48(O18,F19)Sc47 at 275 MeV was measured for the first time, under the NUMEN experimental campaign. Differential cross-section angular distribution measurements for the F19 ejectiles were performed at INFN-LNS in Catania by using the MAGNEX large acceptance magnetic spectrometer. The data were analyzed within the distorted-wave and coupled-channels Born approximation frameworks. The initial and final-state interactions were described adopting the São Paulo potential, whereas the spectroscopic amplitudes for the projectile and target overlaps were derived from shell-model calculations. The theoretical cross sections are found to be in very good agreement with the experimental data, suggesting the validity of the optical potentials and the shell-model description of the involved nuclear states within the adopted model space.1 MoreReceived 27 May 2021Accepted 8 September 2021DOI:https://doi.org/10.1103/PhysRevC.104.034617©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDirect reactionsDouble beta decayLow & intermediate energy heavy-ion reactionsNuclear reactionsTransfer reactionsTechniquesOptical, coupled-channel & distorted wave modelsSpectrometers & spectroscopic techniquesNuclear Physics

Multistep processes in heavy-ion-induced single-nucleon transfer reactions

It was first noted during the 1970s that finite-range distorted wave Born approximation (FR-DWBA) calculations were unable satisfactorily to describe the shape of the angular distributions of many single-proton (and some single-neutron) transfer reactions induced by heavy ions, with calculations shifted to larger angles by up to ~ 4 degrees compared with the data. These reactions exhibited a significant mismatch, either of the reaction Q value or the grazing angular momentum of the entrance and exit channels, and it was speculated that the inclusion of multi-step transfer paths via excited state(s) of the projectile and/or ejectile could compensate for the effect of this mismatch and yield good descriptions of the data by shifting the calculated peaks to smaller angles. However, to date this has not been explicitly demonstrated for many reactions. In this work we show that inclusion of the two-step transfer path via the 4.44-MeV 2+ excited state of the 12C projectile in coupled channel Born approximation calculations enables a good description of the 208Pb(12C,11B)209Bi single-proton stripping data at four incident energies which could not be described by the FR-DWBA. We also show that inclusion of a similar reaction path for the 208Pb(12C,13C)207Pb single-neutron pickup reaction has a relatively minor influence, slightly improving the already good description obtained with the FR-DWBA.

Experimental study of intruder components in light neutron-rich nuclei via single-nucleon transfer reaction

With the development of radioactive beam facilities, studies concerning the shell evolution of unstable nuclei have recently gained prominence. Intruder components, particularly s-wave intrusion, in the low-lying states of light neutron-rich nuclei near N=8 are of importance in the study of shell evolution. The use of single-nucleon transfer reactions in inverse kinematics has been a sensitive tool that can be used to quantitatively investigate the single-particle orbital component of selectively populated states. The spin-parity, spectroscopic factor (or single-particle strength), and effective single-particle energy can all be extracted from such reactions. These observables are often useful to explain the nature of shell evolution, and to constrain, check, and test the parameters used in nuclear structure models. In this article, the experimental studies of the intruder components in low-lying states of neutron-rich nuclei of He, Li, Be, B, and C isotopes using various single-nucleon transfer reactions are reviewed. The focus is laid on the precise determination of the intruder s-wave strength in low-lying states.

Transfer reaction code with nonlocal interactions

We present a suite of codes (NLAT for nonlocal adiabatic transfer) to calculate the transfer cross section for single-nucleon transfer reactions, (d,N) or (N,d), including nonlocal nucleon–target interactions, within the adiabatic distorted wave approximation. For this purpose, we implement an iterative method for solving the second order nonlocal differential equation, for both scattering and bound states. The final observables that can be obtained with NLAT are differential angular distributions for the cross sections of A(d,N)B or B(N,d)A. Details on the implementation of the T-matrix to obtain the final cross sections within the adiabatic distorted wave approximation method are also provided. This code is suitable to be applied for deuteron induced reactions in the range of Ed=10–70MeV, and provides cross sections with 4% accuracy. Program summaryProgram title: NLATCatalogue identifier: AFAY_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AFAY_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: GNU General Public License, version 3No. of lines in distributed program, including test data, etc.: 662136No. of bytes in distributed program, including test data, etc.: 15253066Distribution format: tar.gzProgramming language: Fortran 90.Computer: Dell Poweredge R620 (Intel XEON E5-2650v2) 2.9 GHz Intel Core i5.Operating system: Linux (Debian 7) Mac OSX.RAM: Around 3 GBClassification: 17.8, 17.9, 17.11, 17.16.Nature of problem:Calculates cross sections for deuteron induced single-nucleon transfer reactions using nonlocal potentials within the adiabatic distorted wave approximation.Solution method:See ‘Nature of problem’.Running time:Less than 2 hours. See sample output files without extension for indication of time taken.

Construction and commissioning of the SuperORRUBA detector

The SuperORRUBA (Oak Ridge Rutgers University Barrel Array) of double-sided silicon strip detectors has been constructed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). The array will primarily be used to study single-nucleon transfer reactions in inverse kinematics at exotic beam facilities. The detector exhibits good intrinsic energy resolution (∼25keV) and large solid-angle coverage over the polar angular range 55–125°. The detector is now in routine use and has been used for several measurements at the HRIBF.

Single-nucleon transfer reactions on18F

Simultaneous measurement of the proton-transfer ${}^{18}\mathrm{F}{(d,\phantom{\rule{-0.16em}{0ex}}n)}^{19}\mathrm{Ne}$ and neutron-transfer ${}^{18}\mathrm{F}{(d,\phantom{\rule{-0.16em}{0ex}}p)}^{19}\mathrm{F}$ reactions were performed with a ${}^{18}\mathrm{F}$ radioactive beam at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The experiments clarify the nuclear structure of ${}^{19}\mathrm{Ne}$ near the proton threshold, which is relevant for understanding the rates of proton-induced reactions on ${}^{18}\mathrm{F}$ in novae. Analogs for several states in the mirror nucleus ${}^{19}\mathrm{F}$ have not yet been identified in ${}^{19}\mathrm{Ne}$, indicating that the level structure of ${}^{19}\mathrm{Ne}$ in this region is incomplete. We observed 15 levels in ${}^{19}\mathrm{Ne}$ from the ${}^{18}\mathrm{F}{(d,\phantom{\rule{-0.16em}{0ex}}n)}^{19}\mathrm{Ne}$ measurement and 18 levels in ${}^{19}\mathrm{F}$ from the ${}^{18}\mathrm{F}{(d,\phantom{\rule{-0.16em}{0ex}}p)}^{19}\mathrm{F}$ measurement. Angular distributions were extracted for all strongly populated states and compared to distorted-wave Born approximation calculations. The angular distributions for all the known states in the two nuclei determined in this work are consistent with their previously assigned spins and parities. The spectroscopic factors determined for these levels in the two nuclei are reported.

Lithium induced nuclear reactions of astrophysical interest

Systematic studies of nuclear astrophysical reactions induced by lithium isotopes using the unstable ion beam facility GIRAFFE in CIAE were performed. We have measured the angular distributions of some single nucleon transfer reactions, such as 8Li(d,p) 9Li, 8Li(d,n) 9Be and 8Li(p,d) 7Li in inverse kinematics, and derived the astrophysical S-factors or reaction rates for 8Li(n, γ) 9Li and 8Li(p, γ) 9Be by using asymptotic normalization coefficient (ANC) or spectroscopic factor.

Pairing resonances and the continuum spectroscopy of 10Li

Pairing across the particle emission threshold and the properties of corresponding quasiparticle strength functions are discussed in an extended mean-field approach. This particular type of dynamical correlations gives rise to a unique class of sharp low-lying resonances close to the particle emission threshold. Spectral functions for particle and hole states are discussed. They are explored theoretically by single-nucleon transfer reactions, populating the low energy continuum with respect to a core nucleus. The cross sections of the reaction d(9Li, 10Li)p at Tlab=2.36 AMeV, recently measured at REX-ISOLDE, are well reproduced by our calculations including a pairing resonance in the 3/2− partial wave of purely coupled channels nature.

Isospin dependence of the spin-orbit splitting in nuclei

An analysis has been made of experimental data on level spectra, single-nucleon transfer reactions near closed shells, and data on polarization effects in charge-exchange (p, n) reactions between isoanalogous states of nuclei with even A. The analysis has allowed us to conclude that there is a significant difference between the spin-orbit splittings of neutrons and protons in identical orbitals. This conclusion is confirmed in the framework of different theoretical approaches.

Single nucleon transfer reactions near Coulomb barrier on 197Au

Single neutron transfer reactions on 197Au induced by 12C and 16O at near Coulomb barrier energies have been studied using radiochemical and off-line gamma-ray spectrometric techniques. High spin yield fraction (HSF = σm/(σm+σg)) for 196m,gAu and formation cross section ratio (σ198/σ196) of 198Au and 196Au have been determined for both 197Au+12C and 197Au+16O reactions at different excitation energies near the Coulomb barrier. The HSF of 196m,gAu and σ198/σ196 values in both reactions are seen to sharply increase with increasing excitation energy near the Coulomb barrier and then slowly increase reaching a constant value at high projectile energy. These observations have been analyzed in terms of nuclear structural and kinematic parameters. A comparison the effects of Coulomb excitation and nucleon transfer process during heavy-ion interactions indicates a predominant effect of the latter process in the background of the Coulomb excitation. Observed reaction systematics seem to follow the quasi-elastic transfer process.

Study of transfer reactions in inverse kinematics with the TIARA array

The newly commissioned TIARA array has been coupled for the first time to the VAMOS spectrometer and the EXOGAM germanium array to study nucleon transfer reactions in inverse kinematics and using beams of low intensity, which are typical of radioactive beam experiments. This set-up offers a high geometrical efficiency for the charged particle detection, a high efficiency for γ-ray detection and a final energy resolution only limited by the Doppler broadening. This report demonstrates the potential of such an apparatus to study single-nucleon transfer reactions with radioactive nuclear beams. A beam of 14N at 10.6 MeV/nucleon with an intensity of 105 s−1 was directed onto a CD2 target of 1 mg cm−2. Proton angular distributions have been measured for the population of 15N in the ground state and in excited states at 7.15 and 7.56 MeV. Transferred l-values deduced from comparison to DWBA calculations are in very good agreement with the well-known shell structure of 15N. We have therefore demonstrated the effectiveness of this set-up in studying nucleon transfer reactions in inverse kinematics and with low-intensity beams.

First experiments on transfer with radioactive beams using the TIARA array

Results from a study in inverse kinematics of the 24Ne(d, pγ)25Ne reaction, using a radioactive beam of 24Ne from the SPIRAL facility at GANIL, are reported. First, a brief overview is given of several methods using radioactive beams to study the classic single-nucleon transfer reactions such as (d, p) or (d, t)/(d, 3He), where the experimental design is strongly influenced by the extreme inverse kinematics. A promising approach to deliver good energy resolution is to combine a high geometrical efficiency for kinematically complete charged particle detection with a high efficiency array for gamma-ray detection. One of the first dedicated set-ups for this type of experiment is the TIARA silicon strip array combined with the EXOGAM segmented germanium array. Together they comprise a highly compact, position-sensitive particle array with 90% of 4π coverage, mounted inside a cubic arrangement of four segmented gamma-ray detectors in very close geometry with 67% of 4π active coverage. Using this setup, the structure of 25Ne has been studied via the (d, p) reaction. A pure ISOL beam of 105 s-1 of 24Ne at 10 MeV/A was provided by SPIRAL and bombarded a CD2 target of 1 mg/cm2. The 25Ne was detected at the focal plane of the VAMOS spectrometer where the direct beam was separated and intercepted. Reaction protons were detected in coincidence with little background. Four resolved peaks were recorded between Ex = 0 and 4 MeV. The data confirm and extend the results from a multinucleon transfer study using the (13C,14O) reaction. Further information has been obtained using the energies of coincident gamma-rays. The reactions 24Ne(d, dγ)24Ne, 24Ne(d, t)23Ne and 24Ne(d, 3He)23F were recorded simultaneously and analysis of these is also underway.

Pre-asymptotic behavior of single-particle overlap integrals of non-Borromean two-neutron halos

For non-Borromean two-neutron halo nuclei, modifications to the behavior of single-particle overlap integrals will arise due to the correlations of the two interacting nucleons in the halo. An additional contribution to the overlap integral can be obtained using the Feynman diagram approach. This additional term is modeled using a simple local potential model. We show that these modifications may play a role in detailed interpretations of experimental results from single-nucleon knockout, transfer, and other reactions that probe the single-nucleon overlap functions.

Energy dependence of the total reaction cross section of isomeric18Fmon silicon below 400 MeV

A 25 MeV/nucleon primary O-17 beam was used to produce an isomeric state F-18(m) beam via the single-nucleon transfer reaction O-17 (C-12, B-11)F-18(m). The total nuclear reaction cross section, sigma(R), of F-18(m) (metastable) on silicon was measured using a stack of silicon surface barrier detectors that included a position sensitive silicon detector (PSD). The total reaction cross sections were determined as a function of bombarding energy up to 400 MeV by measuring the energy loss in each detector. The reaction cross sections were measured both for a mixture of metastable- and ground-state ions and for a pure ground-state beam. The reaction cross sections for N-14 and O-16 beams were also measured simultaneously. The reaction cross sections for the metastable beam were deduced from the mixed- and the ground-state cross sections, corrected for the measured purity of the mixed-state beam. The observed reaction cross sections for F-18(m) are larger at low energies than the cross sections measured for the ground state. The isomeric cross sections can be reproduced by an optical model potential having a diffuseness of 0.8 fm, compared to a more conventional diffuseness parameter of 0.5 fm, which is adequate to reproduce the N-14, O-16, and F-18(g.s.) cross sections measured in this experiment.

Single-nucleon knockout reactions at fragmentation beam energies

Single-nucleon knockout reactions show considerable promise as a spectroscopic tool for mapping the migration of the dominant single-particle strength in rare isotopes, produced as fragmentation beams with energies > 40 MeV/nucleon. In this paper the theoretical assumptions which underpin the eikonal theory treatment of these reactions are reviewed. Certain sensitivities to input parameters are discussed, as are the possible importance of classes of higher order corrections. The eikonal model prediction for the elastic breakup component of the nucleon removal cross sections is also compared with that from fully-quantum mechanical calculations using the discretised continuum coupled channels method. An asymmetry, manifest in the experimental longitudinal momentum distributions of the ground state residues in weakly-bound-nucleon removal, is well reproduced. 1. INTRODUCTION An ability to map the evolution of the positions and order of nuclear single particle states in rare nuclei of high isospin will be an important component in developing our understanding and the reliability of structure models in these regions. The low intensities of secondary beams of these species, combined with the small number of excited states available in lighter systems, mean that conventional (but in inverse kinematics) lightion single-nucleon transfer reaction and gamma spectroscopic methods are non-trivial. Nucleon-knockout reactions appear to offer an alternative and complementary technique which is particularly well adapted for rare isotope beams produced using fragmentation. From a reaction theory point of view, it has been extremely fortuitous that many of the first generation facilities for the production of rare unstable nuclei have been based on nuclear fragmentation. The high secondary beam energies, and fast collisions with a secondary target, have allowed a rapid development and application of reaction methods, based on the sudden/adiabatic and/or eikonal-like approximations [1–8]. These lead to considerable simplifications and also practical and accurate calculation schemes which have relatively simple and physically transparent input parameters. This has allowed new experimental results to gain feedback rapidly from theory, and vice versa. Having said this, very little of the extensive literature to date has discussed possible schemes to obtain detailed spectroscopic information from data. To a large extent,

Potential and limitations of nucleon transfer experiments with radioactive beams at REX-ISOLDE

As a tool for studying the structure of nuclei far off stability the technique of gamma-ray spectroscopy after low-energy single-nucleon transfer reactions with radioactive nuclear beams in inverse kinematics was investigated. Modules of the MINIBALL germanium array and a thin position-sensitive parallel plate avalanche counter (PPAC) to be employed in future experiments at REX-ISOLDE were used in a test experiment performed with a stable 36S beam on deuteron and 9Be targets. It is demonstrated that the Doppler broadening of gamma lines detected by the MINIBALL modules is considerably reduced by exploiting their segmentation, and that for beam intensities up to 10^6 particles/s the PPAC positioned around zero degrees with respect to the beam axis allows not only to significantly reduce the gamma background by requiring coincidences with the transfer products but also to control the beam and its intensity by single particle counting. The predicted large neutron pickup cross sections of neutron-rich light nuclei on 2H and 9Be targets at REX-ISOLDE energies of 2.2 MeV A are confirmed.