One-neutron Transfer Reactions Research Articles

The NUMEN project: probing nuclear response to weak interaction by nuclear reactions

Different reactions channels induced by the 18O + 40Ca collisions at 275 MeV incident energy are simultaneously measured and analysed consistently within the same reaction and structure frameworks within the NUMEN project. The project aims to provide data-driven information for the determination of the nuclear matrix elements involved in the neutrinoless double beta decay. In particular, the elastic and inelastic scattering, one- and two-proton transfer, one-neutron transfer, and single charge exchange reactions are explored. The full quantum-mechanical calculations, performed by including microscopic nuclear structure inputs, describe well all the experimental data, giving support to a multi-channel strategy for the analysis of heavy-ion induced direct reactions.

Study of the one-neutron transfer reaction in 18O + 76Se collision at 275 MeV in the context of the NUMEN project

Heavy-ion one-nucleon transfer reactions are promising tools to investigate single-particle configurations in nuclear states, with and without the excitation of the core degrees of freedom. An accurate determination of the spectroscopic amplitudes of these configurations is essential for the study of other direct reactions as well as beta-decays. In this context, the 76Se(18O,17O)77Se one-neutron transfer reaction gives a quantitative access to the relevant single particle orbitals and core polarization transitions built on 76Se. This is particularly relevant, since it provides data-driven information to constrain nuclear structure models for the 76Se nucleus.The excitation energy spectrum and the differential cross section angular distributions of this nucleon transfer reaction was measured at 275 MeV incident energy for the first time using the MAGNEX large acceptance magnetic spectrometer. The data are compared with calculations based on distorted wave Born approximation and coupled channel Born approximation adopting spectroscopic amplitudes for the projectile and target overlaps derived by large-scale shell model calculations and interacting boson-fermion model.These reactions are studied in the frame of the NUMEN project. The NUMEN (NUclear Matrix Elements for Neutrinoless double beta decay) project was conceived at the Istituto Nazionale di Fisica Nucleare–Laboratori Nazionali del Sud (INFN-LNS) in Catania, Italy, aiming at accessing information about the nuclear matrix elements (NME) of neutrinoless double beta decay (0νββ) through the study of the heavy-ion induced double charge exchange (DCE) reactions on various 0νββ decay candidate targets. Among these, the 76Se nucleus is under investigation since it is the daughter nucleus of 76Ge in the 0νββ decay process.

Halo effects in the Li11(p,t)Li9 reaction

I investigate the $^{11}\mathrm{Li}(p,t)^{9}\mathrm{Li}$ two-neutron transfer reaction at ${E}_{\mathrm{lab}}=33$ MeV within the distorted wave Born approximation (DWBA). The $^{11}\mathrm{Li}$ and $^{3}\mathrm{H}$ nuclei are described in the hyperspherical formalism, as $^{9}\mathrm{Li}\phantom{\rule{0.16em}{0ex}}+\phantom{\rule{0.16em}{0ex}}n+n$ and $p+n+n$ configurations, respectively. The calculation of the cross section is shown to be much more complicated than in one-neutron transfer reactions, owing to the three-body structure of $^{11}\mathrm{Li}$. The $^{11}\mathrm{Li}\phantom{\rule{0.16em}{0ex}}+\phantom{\rule{0.16em}{0ex}}p$ and $^{9}\mathrm{Li}\phantom{\rule{0.16em}{0ex}}+\phantom{\rule{0.16em}{0ex}}t$ scattering wave functions are determined with the continuum discretized coupled channel (CDCC) method. Approximations derived from equivalent local potentials are used to compute the transfer cross section at the DWBA. The model reproduces experimental data reasonably well, considering that there is no adjustable parameter. I show that the cross section is fairly sensitive to the long-range part of the $^{11}\mathrm{Li}$ wave function, and therefore to its halo structure.

Evaluation of the K35(p,γ)Ca36 reaction rate using the Ca37(p,d)Ca36 transfer reaction

Background: A recent sensitivity study has shown that the K35(p,γ)Ca36 reaction is one of the ten (p,γ) reaction rates that could significantly impact the shape of the calculated x-ray burst light curve. Its reaction rate used up to now in type I x-ray burst calculations was estimated using an old measurement for the mass of Ca36 and theoretical predictions for the partial decay widths of the first 2+ resonance with arbitrary uncertainties. Purpose: In this work, we propose to reinvestigate the K35(p,γ)Ca36 reaction rate, as well as related uncertainties, by determining the energies and decay branching ratios of Ca36 levels, within the Gamow window of x-ray bursts, in the 0.5 to 2 GK temperature range. Method: These properties were studied by means of the one-neutron pickup transfer reaction Ca37(p,d)Ca36 in inverse kinematics using a radioactive beam of Ca37 at 48 MeV nucleon−1. The experiment was performed at the GANIL facility using the liquid hydrogen target CRYPTA, the MUST2 charged particle detector array for the detection of the light charged particles, and a zero degree detection system for the outgoing heavy recoil nuclei. Results: The atomic mass of Ca36 is confirmed and new resonances have been proposed together with their proton decay branching ratios. This spectroscopic information, used in combination with very recent theoretical predictions for the γ-decay width, were used to calculate the K35(p,γ)Ca36 reaction rate. The recommended rate of the present work was obtained within a uncertainty factor of 2 at 1σ. This is consistent with the previous estimate in the x-ray burst temperature range. A large increase of the reaction rate was found at higher temperatures due to two newly discovered resonances. Conclusions: The K35(p,γ)Ca36 thermonuclear reaction rate is now well constrained by the present work in a broad range of temperatures covering those relevant to type I x-ray bursts. Our results show that the K35(p,γ)Ca36 reaction does not affect the shape of the x-ray burst light curve, and that it can be removed from the list of the few influential proton radiative captures reactions having a strong impact on the light curve.Received 18 January 2021Accepted 12 April 2021DOI:https://doi.org/10.1103/PhysRevC.103.055809©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDirect reactionsExplosive burningNuclear astrophysicsNuclear physics of explosive environmentsNucleon induced nuclear reactionsProton emissionRadiative captureTransfer reactionsProperties20 ≤ A ≤ 38Nuclear PhysicsGravitation, Cosmology & Astrophysics

Observation of the near-threshold intruder 0− resonance in Be12

A resonant state at $3.21^{+0.12}_{-0.04}$\,MeV, located just above the one-neutron separation threshold, was observed for the first time in $^{12}$Be from the $^{11}$Be\,$(d,p)^{12}$Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^-$, according to the distorted-wave Born approximation (DWBA) and decay-width analysis. Gamow coupled-channel (GCC) and Gamow shell-model (GSM) calculations show the importance of the continuum-coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in $^{12}$Be and in its isotonic nucleus $^{11}$Li are comparably discussed.

Scission configuration of U239 from yields and kinetic information of fission fragments

The simultaneous measurement of the isotopic fission-fragment yields and fission-fragment velocities of $^{239}$U has been performed for the first time. The $^{239}$U fissioning system was produced in one-neutron transfer reactions between a $^{238}$U beam at 5.88 MeV/nucleon and a $^{9}$Be target. The combination of inverse kinematics at low energy and the use of the VAMOS++ spectrometer at the GANIL facility allows the isotopic identification of the full fission-fragment distribution and their velocity in the reference frame of the fissioning system. The proton and neutron content of the fragments at scission, their total kinetic and total excitation energy, as well as the neutron multiplicity were determined. Information from the scission point configuration is obtained from these observables and the correlation between them. The role of the octupole-deformed proton and neutron shells in the fission-fragment production is discussed.

Impact of uncertainties of unbound 10Li on the ground state of two-neutron halo 11Li

Recently, the energy spectrum of \boldsymbol{^{10}}10Li was measured upto \boldsymbol{4.6}4.6 MeV, via one-neutron transfer reaction \boldsymbol{d(^{9}\textrm{Li},~p)^{10}\textrm{Li}}𝐝(9Li,𝐩)10Li. Considering the ambiguities on the \boldsymbol{^{10}}10Li continuum spectrum with reference to new data, we report the configuration mixing in the ground state of the two-neutron halo nucleus \boldsymbol{^{11}}11Li for two different choices of the \boldsymbol{^{9}{\textrm{Li}}+n}9Li+𝐧 potential. For the present study, we employ a three-body (\boldsymbol{\textrm{core}+n+n}core+𝐧+𝐧) structure model developed for describing the two-neutron halo system by explicit coupling of unbound continuum states of the subsystem (\boldsymbol{\textrm{core}+n}core+𝐧), and discuss the two-neutron correlations in the ground state of \boldsymbol{^{11}}11Li.

First Direct Measurement of Isotopic Fission-Fragment Yields of ^{239}U.

A direct and complete measurement of isotopic fission-fragment yields of ^{239}U has been performed for the first time. The ^{239}U fissioning system was produced with an average excitation energy of 8.3MeV in one-neutron transfer reactions between a ^{238}U beam and a ^{9}Be target at Coulomb barrier energies. The fission fragments were detected and isotopically identified using the VAMOS++ spectrometer at the GANIL facility. The measurement allows us to directly evaluate the fission models at excitation energies of fast neutrons, which are relevant for next-generation nuclear reactors. The present data, in agreement with model calculations, do not support the recently reported anomaly in the fission-fragment yields of ^{239}U, and they confirm the persistence of spherical shell effects in the Sn region at excitation energies exceeding the fission barrier by a few mega-electron volts.

Elastic scattering of the B12+Ni58 system at near-barrier energies

Elastic scattering of a radioactive neutron-rich boron isotope, $^{12}\mathrm{B}$, has been measured for the first time. Angular distributions for the elastic scattering of $^{12}\mathrm{B}+^{58}\mathrm{Ni}$ have been measured at ${\mathit{E}}_{\mathrm{Lab}}=30.0$ and 33.0 MeV, which are just above the Coulomb barrier (${\mathit{V}}_{\mathrm{B}}=24$ MeV). The obtained angular distributions were analyzed in terms of the large-scale coupled channel (CC) and coupled reaction channel (CRC) calculations, where several inelastic transitions for the target, as well as the most relevant transfer reactions, have been included in the coupling matrix elements. The roles of the spin reorientation and spin-orbit interaction in the reaction mechanism were also investigated. The one-neutron transfer reaction through a coupled reaction calculation had some effect on the elastic scattering of the system studied.

A New Measurement of 11Be(p,d) Transfer Reaction**Supported by the National Key Research and Development Program of China under Grant No 2018YFA0404403, and the National Natural Science Foundation of China under Grant Nos 11775004 and 11775036.

A new 11Be(p,d) transfer reaction experiment is performed in inverse kinematics with a radioactive 11Be beam at 26.9A MeV. Three low-lying states, namely the 0+ ground state, the 2+ state at Ex = 3.37 MeV, and the multiplet at around 6 MeV in 10Be, are populated by this one-neutron transfer reaction. These three states in 10Be are clearly discriminated from the Q-value spectrum, which is rebuilt from energies and angles of the recoil deuterons in coincidence with 10Be. A spectroscopic factor for each state is extracted by comparing the experimental differential cross sections to the theoretical calculation results using the finite range adiabatic distorted wave approximation method with different global nucleon-nucleus potentials. It is found that the newly extracted spectroscopic factors for the 0+ and 2+ states are consistent with the previous ones, but the factor for the multiplet is smaller than the value in the reference, and the possible reason is discussed.

Low-lying states in Be12 using one-neutron transfer reaction

Low-lying states in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Be</mml:mi><mml:mprescripts /><mml:none /><mml:mn>12</mml:mn></mml:mmultiscripts></mml:math> using one-neutron transfer reaction

Sub-barrier fusion of weakly bound Li6 with Ni58

Evaporation-proton yields were measured for the fusion of the weakly bound nucleus $^{6}\mathrm{Li}$ on a $^{58}\mathrm{Ni}$ target at six near- or sub-barrier bombarding energies. Effects of the one-neutron transfer reaction were estimated and corrections made. Total-fusion cross sections were deduced using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential. Inelastic couplings are estimated to have insignificant effects on such fusion. The sum of total fusion plus one-neutron transfer cross sections nearly saturates the total reaction cross section in the energy region measured. Comparison with previous results appropriately scaled for the $^{6}\mathrm{Li}+(^{59}\mathrm{Co}, ^{64}\mathrm{Ni}, ^{64}\mathrm{Zn})$ systems shows good consistency except for some data spread at the lower energies.

Examination of the adiabatic approximation for (d,p) reactions

Background: Deuteron-induced one-neutron transfer reactions have been used to extract single-particle properties of nuclei, and the adiabatic (AD) approximation is often used to simply treat the deuteron breakup states. Purpose: The primary goal is to examine the validity of the AD approximation for the ($d,p$) reaction systematically. We clarify also the role of the closed-channels often ignored in the description of breakup reactions. Methods: We calculate the ($d,p$) cross sections with the continuum-discretized coupled-channels method (CDCC) for 128 reactions systems and compare the results with those obtained by the CDCC calculation with the AD approximation. Effect of the closed channels are investigated by ignoring the closed channels in CDCC. Results: The AD approximation affects in general the ($d,p$) cross section by less than 20 %, but some exceptional nonadiabatic cases for which the AD approximation breaks down are found. The closed channels turn out to give significant effects on the cross section at deuteron energies less than about 10 MeV. Conclusions: The use of the AD approximation in the description of the ($d,p$) reaction can be justified in many cases, with the uncertainty of less than about 20 %. The existence of some nonadiabatic cases nevertheless should be realized. The neglect of the closed channels without confirming the convergence of the CDCC result is not recommended.

Investigation of the ^{10}Li shell inversion by neutron continuum transfer reaction.

This Letter reports a study of the highly debated ^{10}Li structure through the d(^{9}Li,p)^{10}Li one-neutron transfer reaction at 100MeV. The ^{10}Li energy spectrum is measured up to 4.6MeV and angular distributions corresponding to different excitation energy regions are reported for the first time. The comparison between data and theoretical predictions, including pairing correlation effects, shows the existence of a p_{1/2} resonance at 0.45±0.03 MeV excitation energy, while no evidence for a significant s-wave contribution close to the threshold energy is observed. Moreover, two high-lying structures are populated at 1.5 and 2.9MeV. The corresponding angular distributions suggest a significant s_{1/2} partial-wave contribution for the 1.5MeV structure and a mixing of configurations at higher energy, with the d_{5/2} partial-wave contributing the most to the cross section.

Investigation of the role of 10Li resonances in the halo structure of 11Li through the Li11(p,d)Li10 transfer reaction

Abstract The first measurement of the one-neutron transfer reaction 11Li(p,d)10Li performed using the IRIS facility at TRIUMF with a 5.7 A MeV 11Li beam interacting with a solid H2 target is reported. The 10Li residue was populated strongly as a resonance peak with energy E r = 0.62 ± 0.04 MeV having a total width Γ = 0.33 ± 0.07 MeV . The angular distribution of this resonance is characterized by neutron occupying the 1 p 1 / 2 orbital. A DWBA analysis yields a spectroscopic factor of 0.67 ± 0.12 for p 1 / 2 removal strength from the ground state of 11Li to the region of the peak.

Preliminary study of the10Li nucleus via one-neutron transfer

The structure of the 10 Li unbound nucleus is a subject of large interest and its description is nowadays a matter of debate. We have investigated this system using the d( 9 Li,p) 10 Li one-neutron transfer reaction at 100 MeV in inverse kinematics. The experiment was performed at the ISACII facility at TRIUMF laboratory. The excitation energy spectrum has been reconstructed by measuring the emitted protons at backward angles and the 9 Li at forward angles.

Background considerations for the 2H(7Be,3H)6Be experimental data II: Three-body continuum

The present article reports second background considerations for the experimentally obtained 2H(7Be,3H)6Be differential cross sections. The one-neutron transfer reaction was measured in inverse kinematics by using radioactive 7Be (t 1/2 = 53.2 days) beams at the Holifield Radioactive Ion Beam Facility of the Oak Ridge National Laboratory in 2004 in order to search for the resonances in the unbound 6Be nucleus. Resonances in this nucleus would affect the 3He(3He,2 p)4He reaction rate of the proton-proton chain occurring in stars such as our sun. The result shows, however, that the direct transfer to 6Be resonances is not particularly strong compared to other reaction channels that can produce tritons in the exit channels. The goals of the present work is to better understand the cross section data from transfer reaction measurements by adopting background considerations using the three-body continuum.

Experimental study of theNi66(d,p) Ni67one-neutron transfer reaction

The quasi-SU(3) sequence of the positive parity νg9/2,d5/2,s1/2 orbitals above the N=40 shell gap are assumed to induce strong quadrupole collectivity in the neutron-rich Fe (Z=26) and Cr (Z=24) isotopes below the nickel region. In this paper the position and strength of these single-particle orbitals are characterized in the neighborhood of Ni68 (Z=28,N=40) through the Ni66(d,p)Ni67 one-neutron transfer reaction at 2.95 MeV/nucleon in inverse kinematics, performed at the REX-ISOLDE facility in CERN. A combination of the Miniball γ-array and T-REX particle-detection setup was used and a delayed coincidence technique was employed to investigate the 13.3-μs isomer at 1007 keV in Ni67. Excited states up to an excitation energy of 5.8 MeV have been populated. Feeding of the νg9/2 (1007 keV) and νd5/2 (2207 keV and 3277 keV) positive-parity neutron states and negative parity (νpf) states have been observed at low excitation energy. The extracted relative spectroscopic factors, based on a distorted-wave Born approximation analysis, show that the νd5/2 single-particle strength is mostly split over these two excited states. The results are also compared to the distribution of the proton single-particle strength in the Zr90 region (Z=40,N=50).6 MoreReceived 25 February 2015Revised 28 April 2015DOI:https://doi.org/10.1103/PhysRevC.91.054321This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical Society

Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z=50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, N=82, and neutron-deficient, N=50, regions. Here we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in 131Sn from across the N=82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient 106,108Sn. In both cases, measurements of gamma rays in coincidence with charged particles proved to be invaluable.

Study of the Pygmy Dipole Resonance in (p,p’γ) and (d,pγ) experiments with SONIC@HORUS

Last year, the new silicon-detector array SONIC with up to 8 silicon-detector positions was in- stalled inside the existing γ-ray spectrometer HORUS consisting of 14 HPGe detectors. The combined setup SONIC@HORUS allows for a coincident detection of γ-rays and light charged particles in the exit channel of inelastic scattering and transfer reactions. As a first physics case, the Pygmy Dipole Resonance (PDR) in 92 Mo has been investigated in a (p,p'γ) experiment at E p = 10.5 MeV. Since a specific excitation energy can be chosen offline in the coincidence data, the sensitivity to weak decay branchings of PDR states is increased. Additionally, a second reaction mechanism for the excitation of PDR states has been tested with the new setup. In a 119 Sn(d,pγ) transfer reaction at Ed = 8.5 MeV, PDR states in 120 Sn could be excited. Since this one-neutron transfer reaction is sensitive to the neutron single-particle structure, it could reveal new information on the microscopic structure of the PDR.