A digital data-acquisition system based on XIA LLC products was used in a complex nuclear reaction experiment using radioactive ion beams.A flexible trigger system based on a field-programmable gate array(FPGA)paramet...A digital data-acquisition system based on XIA LLC products was used in a complex nuclear reaction experiment using radioactive ion beams.A flexible trigger system based on a field-programmable gate array(FPGA)parametrization was developed to adapt to different experimental sizes.A user-friendly interface was implemented,which allows converting script language expressions into FPGA internal control parameters.The proposed digital system can be combined with a conventional analog data acquisition system to provide more flexibility.The performance of the combined system was veri-fied using experimental data.展开更多
Clustering is a general phenomenon observed in light nuclei, especially in neutron-rich nuclei in which molecular configurations can be formed with various combinations of valence neutrons. Thus far, many theoretical ...Clustering is a general phenomenon observed in light nuclei, especially in neutron-rich nuclei in which molecular configurations can be formed with various combinations of valence neutrons. Thus far, many theoretical models have been developed to describe nuclear clustering phenomena. These models are outlined in this review article, with an emphasis on their basic formulations and physical ingredients. In addition, various experimental tools, such as inelastic excitation and decay, transfer reactions, and resonant scattering reactions, have been applied to investigate the cluster structures inside the nucleus. Each tool possesses certain advantages and favorable applications, which are also described. In the case of neutron-rich nuclei, cluster structures may be configured as molecular states that form rotational bands with an extremely large moment of inertia and generate relatively large cluster decay width. The major experimental criteria for the identification of cluster formation are discussed herein.展开更多
Collinear laser spectroscopy is a powerful tool for studying the nuclear spins,electromagnetic moments,and charge radii of exotic nuclei.To study the nuclear properties of unstable nuclei at the Beijing Radioactive Io...Collinear laser spectroscopy is a powerful tool for studying the nuclear spins,electromagnetic moments,and charge radii of exotic nuclei.To study the nuclear properties of unstable nuclei at the Beijing Radioactive Ion-beam Facility(BRIF)and the future High Intensity Heavy-ion Accelerator Facility(HIAF),we developed a collinear laser spectroscopy apparatus integrated with an offline laser ablation ion source and a laser system.The overall performance of this state-of-the-art technique was evaluated,and the system was commissioned using a bunched stable ion beam.The high-resolution optical spectra for the 4s ^(2)S_(1/2)→4p^(2)P_(3/2)(D2)ionic transition of ^(40;42;44;48)Ca isotopes were successfully measured.The extracted isotope shifts relative to ^(40)Ca showed excellent agreement with the literature values.This system is now ready for use at radioactive ion beam facilities such as the BRIF and paves the way for the further development of higher-sensitivity collinear resonance ionization spectroscopy techniques.展开更多
A gas detector 140×140×140 mm^(3)in size,termed the compact active target time projection chamber(CAT-TPC),was developed in this study to measure resonant scattering associated with cluster structures in uns...A gas detector 140×140×140 mm^(3)in size,termed the compact active target time projection chamber(CAT-TPC),was developed in this study to measure resonant scattering associated with cluster structures in unstable nuclei.The CAT-TPC consists of an electronic field cage,double-thick gas-electron-multiplier foils,a general-purpose digital data acquisition system,and a newly developed two-dimensional strip-readout structure.The CAT-TPC was operated using a^(4)He(96%)+CO_(2)(4%)gas mixture at 400 mbar.The working gas also serves as an active target for tracking charged particles.The overall performance of the CAT-TPC was evaluated using a collimated a-particle source.A time resolution of less than 20 ns and a position resolution of less than 0.2 mm were observed along the electron drift direction.Threedimensional images of incident trajectories and scattering events can be clearly reconstructed under an angular resolution of approximately 0.45 degree.展开更多
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 o...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 singleparticle 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 lowlying 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.展开更多
A small prototype of an active-target time projection chamber detector based on the gas electron multiplier(GEM) readout technique was designed and constructed.Simulation calculations were performed to analyze the ele...A small prototype of an active-target time projection chamber detector based on the gas electron multiplier(GEM) readout technique was designed and constructed.Simulation calculations were performed to analyze the electric field distribution and optimize the design.In particular,a guard ring installed above the GEM foil may play an important role in shaping the electric field in the gas vessel and improving the overall performance of the detector.The best results were obtained at a guard-ring voltage of-950 V.By using a collimated a-particle source,an energy resolution of 3.6–4.0 ke V can be achieved for deposited energies of 18–21 keV,respectively.A position resolution of less 0.2 mm was observed along the electron drift direction,whereas the resolution in the readout plane was approximately 0.45 mm.A time resolution of less than 20 ns was obtained.By using helium as the primary working gas as well as the target material,a t a elastic scattering events can be clearly imaged.展开更多
In this study,we constructed two annular detector arrays comprising 24 wedge-shaped CsI(Tl) crystals,and tested them using anαsource and radioactive beams of ^(14-16) Con a CD_2 target.We compared the properties of a...In this study,we constructed two annular detector arrays comprising 24 wedge-shaped CsI(Tl) crystals,and tested them using anαsource and radioactive beams of ^(14-16) Con a CD_2 target.We compared the properties of a CsI(Tl) crystal encapsulated with various reflectors,revealing that using the 80-μm-thick ESR film to pack the CsI(Tl) crystal yielded the largest light output with the smallest non-uniformity in light output (ΔLO).For the 24 CsI(Tl) detectors with the 80-μm-thick ESR films,the average energy resolution improved as the average light output increased;however,it deteriorated as theΔLO value increased.To form two annular Si-CsI(Tl) telescopes for identifying the light-charged particles,theΔLO value and energy resolution of each CsI(Tl) detector were maintained under 20%and 7.7%,respectively.These telescopes were tested for the first time in a direct nuclear reaction experiment using ^(14-16) C+d.The results demonstrated that the Z=1 and Z=2 charged particles were adequately discriminated by the telescopes using the standardΔE-E method.展开更多
A control and data acquisition system was implemented for the recently developed collinear laser spectroscopy setup.This system is dedicated to data recording,storage,processing,monitoring of the beam intensity and en...A control and data acquisition system was implemented for the recently developed collinear laser spectroscopy setup.This system is dedicated to data recording,storage,processing,monitoring of the beam intensity and energy,and visualization of various spectra.In comparison to the conventional resonance nuclear reaction system,the key technique is the precise synchronization of the detected counts with the actual scanning voltage(or probing laser frequency).The functions of the system were tested by measuring the hyperfine structure spectra of stable calcium(e.g.,^(40)Ca^(+))and radioactive potassium(e.g.,^(38)K)in the bunched and continuous modes,respectively.This system will be routinely applied and further improved in subsequent laser spectroscopy experiments on unstable isotopes at the Beijing Radioactive Ion-beam Facility(BRIF).展开更多
Traditional "magic numbers" were once regarded as immutable throughout the nuclear chart. However, unexpected changes were found for unstable nuclei around N = 20. With both proton and neutron numbers around...Traditional "magic numbers" were once regarded as immutable throughout the nuclear chart. However, unexpected changes were found for unstable nuclei around N = 20. With both proton and neutron numbers around the magic number of 20, the neutron-rich ^(39)Cl isotope provides a good test case for the study of the quantumstate evolution across the major shell. In the present work, the negative parity states in ^(39)Cl are investigated through the β decay spectroscopy of 39 S. Newly observed γ transitions together with a new state are assigned into the level scheme of ^(39)Cl. The spin parity of 5/2^- for the lowest negative parity state in ^(39)Cl is reconfirmed using the combined γ transition information. These systematic observations of the negative parity states in ^(39)Cl allow a comprehensive comparison with the theoretical descriptions. The lowest 5/2^- state in ^(39)Cl remains exotic in terms of comparisons with existing theoretical calculations and with the neighboring isotopes having similar single-particle configurations. Further experimental and theoretical investigations are suggested.展开更多
A new ^11Be（p,d） transfer reaction experiment is performed in inverse kinematics with a radioactive11 Be beam at26.9 MeV. Three low-lying states, namely the 0＋ground state, the 2^＋ state at Ex = 3.37 MeV, and the ...A new ^11Be（p,d） transfer reaction experiment is performed in inverse kinematics with a radioactive11 Be beam at26.9 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 in10 Be, are populated by this one-neutron transfer reaction. These three states in10 Be are clearly discriminated from the -value spectrum, which is rebuilt from energies and angles of the recoil deuterons in coincidence with10 Be. 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.展开更多
Understanding the exotic structure of unstable nuclei is a key focus in nuclear physics,as it is crucial for gaining deeper insights into nuclear forces and behavior of microscopic quantum many-body systems[1].The bas...Understanding the exotic structure of unstable nuclei is a key focus in nuclear physics,as it is crucial for gaining deeper insights into nuclear forces and behavior of microscopic quantum many-body systems[1].The basic properties of unstable nuclei are strongly related to nuclear structure and nucleon-nucleon interaction,making them essential for exploring various novel phenomena that emerge in exotic nuclei.展开更多
Invariant-mass spectroscopy has been performed to search for possible resonance states in the loosely bound neutron-rich15C nucleus.By detecting alpha and11Be in coincidence,we reconstruct the excitation energy spectr...Invariant-mass spectroscopy has been performed to search for possible resonance states in the loosely bound neutron-rich15C nucleus.By detecting alpha and11Be in coincidence,we reconstruct the excitation energy spectrum for15C.To estimate the physical background from non-resonant prompt alpha particles,we employ a recently proposed weighted event-mixing method with phenomenological reduced weighting at around the alpha-decay threshold to account for the depletion in the prompt alpha's contribution owing likely to the Coulomb final-state interactions.A new weighted mixed-event method that focuses on a robust treatment of the Coulomb effect is also proposed.Through fitting the spectrum using the background estimated with these two methods,up to two resonance state candidates are proposed.Further experiments with improved statistics and theoretical calculations are called for to confirm the se resonance states.展开更多
A new inelastic excitation and cluster-decay experiment was conducted to investigate the negative-parity linear-chain structure in 16C.The helium and beryllium isotopes emitted from the highly excited states of 16C an...A new inelastic excitation and cluster-decay experiment was conducted to investigate the negative-parity linear-chain structure in 16C.The helium and beryllium isotopes emitted from the highly excited states of 16C and the recoil target deuteron were detected in coincidence.The 16C excitation-energy spectra associated with different decay paths were reconstructed using the invariant mass method.Owing to the newly reconfigured detector setup,the detection acceptance was extended to a higher excitation-energy range,allowing a number of new resonant states to be observed beyond the previously reportedπ^(2)σ^(2)-bond positive-parity linear-chain band.Based on comparison with the AMD calculations for both resonance energies and relative decay widths,these newly observed states can be tentatively assigned as the 1^(-),3^(-),5^(-)and 1^(-)members of the negative-parity linear-chain molecular rotational band.More experimental studies are expected to directly measure the spins of these states.展开更多
In the excitation of the resonant state followed by the sequential cluster-decay, the in-plane angular correlation method is usually employed to determine the spin of the mother nucleus. However, the correlation patte...In the excitation of the resonant state followed by the sequential cluster-decay, the in-plane angular correlation method is usually employed to determine the spin of the mother nucleus. However, the correlation pattern exhibited in a two-dimensional angular-correlation spectrum depends on the selected coordinate system. In particular, the parity-symmetric and axial-symmetric processes should be presented in a way to enhance the correlation pattern, whereas the non-symmetric process should be plotted separately to reduce the background. In this study, three coordinate systems previously adopted for correlation patterns in the literature are described and compared to each other. The consistency among these systems is evaluated based on the experimental data analysis for the 10.29-MeV state in ^18O. A spin-parity of 4^+ is obtained for all three coordinate systems.展开更多
A^(6)Li(^(16)O,^(19)Ne^(∗))^(3)H multi-nucleon transfer-reaction experiment was performed to populate the highly excited states in^(19)Ne.The subsequent decay particles,^(4)He or protons from the^(19)Ne resonant state...A^(6)Li(^(16)O,^(19)Ne^(∗))^(3)H multi-nucleon transfer-reaction experiment was performed to populate the highly excited states in^(19)Ne.The subsequent decay particles,^(4)He or protons from the^(19)Ne resonant states,were detected in coincidence with the recoil 3 H.The excitation-energy spectra of^(19)Ne were reconstructed using the detected proton or^(4)He and the deduced^(18)F or^(15)O data,respectively.A broad resonance at about 7.85 MeV(1/2^(+))was observed,with partial decay widths different from the previously reported values,which may have a significant impact on the destruction of 18 F in astrophysical processes.Several resonances up to very high excitation energies have been identified with a largeα-clustering strength,which confirm the formation of the cluster structure with a one-hole configuration in light nuclei and encourage further systematic studies of the cluster structure in^(19)Ne.展开更多
A multi-nucleon transfer and cluster decay experiment,^(7)Li(^(11)B,^(14)C^(*)→α+^(10)Be)α,is conducted at an incident beam energy of 55 MeV.This reaction channel has a significantly large 0-value,which favors popu...A multi-nucleon transfer and cluster decay experiment,^(7)Li(^(11)B,^(14)C^(*)→α+^(10)Be)α,is conducted at an incident beam energy of 55 MeV.This reaction channel has a significantly large 0-value,which favors populating the high lying resonant states in ^(14)C.The decay paths,from these resonances to various states of the final nucleus ^(10) Be,can be selected,owing to the experimentally achieved optimal resolution of the Q-value spectrum.A number of resonant states are reconstructed from the forward emitting 10Be+α fragments,and their major molecular structures can be detected according to the selective decay paths and relative decay widths.A state at 22.4(2)MeV validates the previously measured and theoretically predicted band head of the positive-parity σ-bond linear-chain mo-lecular band.Two additional resonances at 22.9(2)and 24.2(2)MeV are identified and consistent with the predicted 2^(+) and 4^(+) members of the same molecular band,thus providing novel evidences for the existence of the exotic clustering chain structure in neutron-rich carbon isotopes.A few high energy resonances,which also indicate the presence of the σ-bond molecular structure,are observed;however,further studies are still required to clarify their ascription in band systematics.展开更多
An experiment for m p（14C},14C＊→10Be＋α）p inelastic excitation and decay was performed in inverse kinematics at a beam energy of 25.3 MeV/u. A series of 14C excited states, including a new one at 18.3（1） MeV, w...An experiment for m p（14C},14C＊→10Be＋α）p inelastic excitation and decay was performed in inverse kinematics at a beam energy of 25.3 MeV/u. A series of 14C excited states, including a new one at 18.3（1） MeV, were observed which decay to various states of the final nucleus of 10Be. A specially designed telescope system, installed around zero degrees, played an essential role in detecting the resonant states near the α-separation threshold. A state at 14.1（1） MeV is clearly identified, being consistent with the predicted band-head of the molecular rotational band characterized by the π-bond linear chain configuration. Further clarification of the properties of this exotic state is suggested by using appropriate reaction tools.展开更多
In order to describe charge exchange reactions at intermediate energies,we implemented as a first step the formulation of the normal eikonal approach.The calculated differential cross-sections based on this approach d...In order to describe charge exchange reactions at intermediate energies,we implemented as a first step the formulation of the normal eikonal approach.The calculated differential cross-sections based on this approach deviated significantly from the conventional DWBA calculations for CE reactions at 140 MeV/nucleon.Thereafter,improvements were made in the application of the eikonal approximation so as to keep a strict three-dimensional form factor.The results obtained with the improved eikonal approach are in good agreement with the DWBA calculations and with the experimental data.Since the improved eikonal approach can be formulated in a microscopic way,it is easy to apply to CE reactions at higher energies,where the phenomenological DWBA is a priori difficult to use due to the lack,in most cases,of the required phenomenological potentials.展开更多
A transfer reaction and cluster-decay experiment,12C(16O,24Mg→ α+20Ne)α, was performed at a beam energy of 96 MeV. Both recoil and decay α particles were detected in coincidence, allowing us to deduce the energymo...A transfer reaction and cluster-decay experiment,12C(16O,24Mg→ α+20Ne)α, was performed at a beam energy of 96 MeV. Both recoil and decay α particles were detected in coincidence, allowing us to deduce the energymomentum of a20Ne fragment. A number of resonant states of24Mg were reconstructed up to an excitation energy of approximately 30 MeV. Owing to the experimentally achieved excellent resolutions of the Q-value and excitationenergy spectra, the relative decay widths for each resonant state in24Mg to various final states of20Ne were extracted, along with the total decay width. The obtained results provide good testing ground for theoretical descriptions of multiple clustering configurations in24Mg.展开更多
基金This work was supported by the National Key R&D Program of China(Nos.2023YFA1606403 and 2023YFE0101600)the National Natural Science Foundation of China(Nos.12027809,11961141003,U1967201,11875073 and 11875074).
文摘A digital data-acquisition system based on XIA LLC products was used in a complex nuclear reaction experiment using radioactive ion beams.A flexible trigger system based on a field-programmable gate array(FPGA)parametrization was developed to adapt to different experimental sizes.A user-friendly interface was implemented,which allows converting script language expressions into FPGA internal control parameters.The proposed digital system can be combined with a conventional analog data acquisition system to provide more flexibility.The performance of the combined system was veri-fied using experimental data.
基金supported by the National Key R&D Program of China(No.2018YFA0404403)the National Natural Science Foundation of China(Nos.11535004,11875074,11875073,11775004,11775013,11775316)
文摘Clustering is a general phenomenon observed in light nuclei, especially in neutron-rich nuclei in which molecular configurations can be formed with various combinations of valence neutrons. Thus far, many theoretical models have been developed to describe nuclear clustering phenomena. These models are outlined in this review article, with an emphasis on their basic formulations and physical ingredients. In addition, various experimental tools, such as inelastic excitation and decay, transfer reactions, and resonant scattering reactions, have been applied to investigate the cluster structures inside the nucleus. Each tool possesses certain advantages and favorable applications, which are also described. In the case of neutron-rich nuclei, cluster structures may be configured as molecular states that form rotational bands with an extremely large moment of inertia and generate relatively large cluster decay width. The major experimental criteria for the identification of cluster formation are discussed herein.
基金supported by the National Natural Science Foundation of China(Nos.12027809,U1967201,11875073,11875074 and 11961141003)National Key R&D Program of China(No.2018YFA0404403)+1 种基金China National Nuclear Corporation(No.FA18000201)the State Key Laboratory of Nuclear Physics and Technology,Peking University(No.NPT2019ZZ02).
文摘Collinear laser spectroscopy is a powerful tool for studying the nuclear spins,electromagnetic moments,and charge radii of exotic nuclei.To study the nuclear properties of unstable nuclei at the Beijing Radioactive Ion-beam Facility(BRIF)and the future High Intensity Heavy-ion Accelerator Facility(HIAF),we developed a collinear laser spectroscopy apparatus integrated with an offline laser ablation ion source and a laser system.The overall performance of this state-of-the-art technique was evaluated,and the system was commissioned using a bunched stable ion beam.The high-resolution optical spectra for the 4s ^(2)S_(1/2)→4p^(2)P_(3/2)(D2)ionic transition of ^(40;42;44;48)Ca isotopes were successfully measured.The extracted isotope shifts relative to ^(40)Ca showed excellent agreement with the literature values.This system is now ready for use at radioactive ion beam facilities such as the BRIF and paves the way for the further development of higher-sensitivity collinear resonance ionization spectroscopy techniques.
基金supported by the National Key R&D Program of China(No.2018YFA0404403)the National Natural Science Foundation of China(Nos.U1967201,11875074,11875073,and 11961141003)the State Key Laboratory of Nuclear Physics and Technology,PKU(No.NPT2020KFY06)。
文摘A gas detector 140×140×140 mm^(3)in size,termed the compact active target time projection chamber(CAT-TPC),was developed in this study to measure resonant scattering associated with cluster structures in unstable nuclei.The CAT-TPC consists of an electronic field cage,double-thick gas-electron-multiplier foils,a general-purpose digital data acquisition system,and a newly developed two-dimensional strip-readout structure.The CAT-TPC was operated using a^(4)He(96%)+CO_(2)(4%)gas mixture at 400 mbar.The working gas also serves as an active target for tracking charged particles.The overall performance of the CAT-TPC was evaluated using a collimated a-particle source.A time resolution of less than 20 ns and a position resolution of less than 0.2 mm were observed along the electron drift direction.Threedimensional images of incident trajectories and scattering events can be clearly reconstructed under an angular resolution of approximately 0.45 degree.
基金supported by the National Key R&D program of China(No.2018YFA0404403)National Natural Science Foundation of China(Nos.11775004,U1867214,and 11535004)
文摘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 singleparticle 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 lowlying 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.
基金supported by the National Natural Science Foundation of China(Nos.11405005 and 11535004)the National Key R&D Program of China(No.2018YFA0404403)
文摘A small prototype of an active-target time projection chamber detector based on the gas electron multiplier(GEM) readout technique was designed and constructed.Simulation calculations were performed to analyze the electric field distribution and optimize the design.In particular,a guard ring installed above the GEM foil may play an important role in shaping the electric field in the gas vessel and improving the overall performance of the detector.The best results were obtained at a guard-ring voltage of-950 V.By using a collimated a-particle source,an energy resolution of 3.6–4.0 ke V can be achieved for deposited energies of 18–21 keV,respectively.A position resolution of less 0.2 mm was observed along the electron drift direction,whereas the resolution in the readout plane was approximately 0.45 mm.A time resolution of less than 20 ns was obtained.By using helium as the primary working gas as well as the target material,a t a elastic scattering events can be clearly imaged.
基金supported by the National Natural Science Foundation of China (Nos.12275007, U1867214, 11775004)the funding from the State Key Laboratory of Nuclear Physics and Technology,Peking University,China (No. NPT2021ZZ01)funding from heavy Ion Research Facility,Lanzhou,China (No. HIR2021PY002)。
文摘In this study,we constructed two annular detector arrays comprising 24 wedge-shaped CsI(Tl) crystals,and tested them using anαsource and radioactive beams of ^(14-16) Con a CD_2 target.We compared the properties of a CsI(Tl) crystal encapsulated with various reflectors,revealing that using the 80-μm-thick ESR film to pack the CsI(Tl) crystal yielded the largest light output with the smallest non-uniformity in light output (ΔLO).For the 24 CsI(Tl) detectors with the 80-μm-thick ESR films,the average energy resolution improved as the average light output increased;however,it deteriorated as theΔLO value increased.To form two annular Si-CsI(Tl) telescopes for identifying the light-charged particles,theΔLO value and energy resolution of each CsI(Tl) detector were maintained under 20%and 7.7%,respectively.These telescopes were tested for the first time in a direct nuclear reaction experiment using ^(14-16) C+d.The results demonstrated that the Z=1 and Z=2 charged particles were adequately discriminated by the telescopes using the standardΔE-E method.
基金supported by the National Natural Science Foundation of China (Nos.12027809,U1967201,11875073,11875074 and 11961141003)National Key R&D Program of China (No.2018YFA0404403)the State Key Laboratory of Nuclear Physics and Technology,Peking University (Nos.NPT2019ZZ02,NPT2020KFY17).
文摘A control and data acquisition system was implemented for the recently developed collinear laser spectroscopy setup.This system is dedicated to data recording,storage,processing,monitoring of the beam intensity and energy,and visualization of various spectra.In comparison to the conventional resonance nuclear reaction system,the key technique is the precise synchronization of the detected counts with the actual scanning voltage(or probing laser frequency).The functions of the system were tested by measuring the hyperfine structure spectra of stable calcium(e.g.,^(40)Ca^(+))and radioactive potassium(e.g.,^(38)K)in the bunched and continuous modes,respectively.This system will be routinely applied and further improved in subsequent laser spectroscopy experiments on unstable isotopes at the Beijing Radioactive Ion-beam Facility(BRIF).
基金Supported by JSPS and CNRS under the Japan-France Research Cooperative Programthe Grant-in-Aid for Scientific Research on Innovative Areas"Toward new frontiers:Encounter and synergy of state-of-the-art astronomical detectors and exotic quantum beams",JSPS/MEXT KAKENHI under Grant Nos JP18HO3692 and JP18H05462+1 种基金the National Key R&D Program of China(2018YFA0404403)the National Natural Science Foundation of China Nos 11775316,11535004,11875074 and 11875073
文摘Traditional "magic numbers" were once regarded as immutable throughout the nuclear chart. However, unexpected changes were found for unstable nuclei around N = 20. With both proton and neutron numbers around the magic number of 20, the neutron-rich ^(39)Cl isotope provides a good test case for the study of the quantumstate evolution across the major shell. In the present work, the negative parity states in ^(39)Cl are investigated through the β decay spectroscopy of 39 S. Newly observed γ transitions together with a new state are assigned into the level scheme of ^(39)Cl. The spin parity of 5/2^- for the lowest negative parity state in ^(39)Cl is reconfirmed using the combined γ transition information. These systematic observations of the negative parity states in ^(39)Cl allow a comprehensive comparison with the theoretical descriptions. The lowest 5/2^- state in ^(39)Cl remains exotic in terms of comparisons with existing theoretical calculations and with the neighboring isotopes having similar single-particle configurations. Further experimental and theoretical investigations are suggested.
基金Supported by the National Key Research and Development Program of China under Grant No 2018YFA0404403the National Natural Science Foundation of China under Grant Nos 11775004 and 11775036
文摘A new ^11Be（p,d） transfer reaction experiment is performed in inverse kinematics with a radioactive11 Be beam at26.9 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 in10 Be, are populated by this one-neutron transfer reaction. These three states in10 Be are clearly discriminated from the -value spectrum, which is rebuilt from energies and angles of the recoil deuterons in coincidence with10 Be. 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.
基金supported by the National Natural Science Foundation of China(12027809,12350007,and 12305122)the National Key R&D Program of China(2023YFE0101600,2023YFA1606403,and 2022YFA1605100)。
文摘Understanding the exotic structure of unstable nuclei is a key focus in nuclear physics,as it is crucial for gaining deeper insights into nuclear forces and behavior of microscopic quantum many-body systems[1].The basic properties of unstable nuclei are strongly related to nuclear structure and nucleon-nucleon interaction,making them essential for exploring various novel phenomena that emerge in exotic nuclei.
基金Supported partially by the National Natural Science Foundation of China (12175009, 12175280, 12250610193, 11605253, 12275007)National Key Research and Development Program of China (2023YFA1606702)+3 种基金the International Partnership Program of the Chinese Academy of Sciences (016GJHZ2023063GC)Major Science and Technology Projects in Gansu Province (24GD13GA005)the support of the CAS “Light of West China” Programthe support of the Natural Science Foundation of Gansu (23JRRA676)。
文摘Invariant-mass spectroscopy has been performed to search for possible resonance states in the loosely bound neutron-rich15C nucleus.By detecting alpha and11Be in coincidence,we reconstruct the excitation energy spectrum for15C.To estimate the physical background from non-resonant prompt alpha particles,we employ a recently proposed weighted event-mixing method with phenomenological reduced weighting at around the alpha-decay threshold to account for the depletion in the prompt alpha's contribution owing likely to the Coulomb final-state interactions.A new weighted mixed-event method that focuses on a robust treatment of the Coulomb effect is also proposed.Through fitting the spectrum using the background estimated with these two methods,up to two resonance state candidates are proposed.Further experiments with improved statistics and theoretical calculations are called for to confirm the se resonance states.
基金Supported by the National Key R&D Program of China(2023YFA1606403,2023YFE0101600,2022YFA1605100)the National Natural Science Foundation of China(12350007,12275007,12027809)。
文摘A new inelastic excitation and cluster-decay experiment was conducted to investigate the negative-parity linear-chain structure in 16C.The helium and beryllium isotopes emitted from the highly excited states of 16C and the recoil target deuteron were detected in coincidence.The 16C excitation-energy spectra associated with different decay paths were reconstructed using the invariant mass method.Owing to the newly reconfigured detector setup,the detection acceptance was extended to a higher excitation-energy range,allowing a number of new resonant states to be observed beyond the previously reportedπ^(2)σ^(2)-bond positive-parity linear-chain band.Based on comparison with the AMD calculations for both resonance energies and relative decay widths,these newly observed states can be tentatively assigned as the 1^(-),3^(-),5^(-)and 1^(-)members of the negative-parity linear-chain molecular rotational band.More experimental studies are expected to directly measure the spins of these states.
基金Supported by the National Key R&D Program of China(2018YFA0404403)the National Natural Science Foundation of China(11535004,11875074,11775004,11875073)
文摘In the excitation of the resonant state followed by the sequential cluster-decay, the in-plane angular correlation method is usually employed to determine the spin of the mother nucleus. However, the correlation pattern exhibited in a two-dimensional angular-correlation spectrum depends on the selected coordinate system. In particular, the parity-symmetric and axial-symmetric processes should be presented in a way to enhance the correlation pattern, whereas the non-symmetric process should be plotted separately to reduce the background. In this study, three coordinate systems previously adopted for correlation patterns in the literature are described and compared to each other. The consistency among these systems is evaluated based on the experimental data analysis for the 10.29-MeV state in ^18O. A spin-parity of 4^+ is obtained for all three coordinate systems.
基金Supported by the National Key R&D Program of China(2018YFA0404403,2022YFA1602302)the National Natural Science Foundation of China(11875074,11875073,12235020,12027809,11961141003,U1967201,U2167204,11775004,11775003)+2 种基金the Continuous Basic Scientific Research Project(WDJC-2019-13)the State Key Laboratory of Nuclear Physics and Technology,Peking University(NPT2020KFY10)the Leading Innovation Project(LC192209000701,LC202309000201)。
文摘A^(6)Li(^(16)O,^(19)Ne^(∗))^(3)H multi-nucleon transfer-reaction experiment was performed to populate the highly excited states in^(19)Ne.The subsequent decay particles,^(4)He or protons from the^(19)Ne resonant states,were detected in coincidence with the recoil 3 H.The excitation-energy spectra of^(19)Ne were reconstructed using the detected proton or^(4)He and the deduced^(18)F or^(15)O data,respectively.A broad resonance at about 7.85 MeV(1/2^(+))was observed,with partial decay widths different from the previously reported values,which may have a significant impact on the destruction of 18 F in astrophysical processes.Several resonances up to very high excitation energies have been identified with a largeα-clustering strength,which confirm the formation of the cluster structure with a one-hole configuration in light nuclei and encourage further systematic studies of the cluster structure in^(19)Ne.
基金Supported by the National Key research and development Program of China(2018YFA0404403)the National Natural Science Foundation of China(11875074,11875073,12027809,11635015,11961141003)the Continuous Basic Scientific Research Project(WDJC-2019-13)。
文摘A multi-nucleon transfer and cluster decay experiment,^(7)Li(^(11)B,^(14)C^(*)→α+^(10)Be)α,is conducted at an incident beam energy of 55 MeV.This reaction channel has a significantly large 0-value,which favors populating the high lying resonant states in ^(14)C.The decay paths,from these resonances to various states of the final nucleus ^(10) Be,can be selected,owing to the experimentally achieved optimal resolution of the Q-value spectrum.A number of resonant states are reconstructed from the forward emitting 10Be+α fragments,and their major molecular structures can be detected according to the selective decay paths and relative decay widths.A state at 22.4(2)MeV validates the previously measured and theoretically predicted band head of the positive-parity σ-bond linear-chain mo-lecular band.Two additional resonances at 22.9(2)and 24.2(2)MeV are identified and consistent with the predicted 2^(+) and 4^(+) members of the same molecular band,thus providing novel evidences for the existence of the exotic clustering chain structure in neutron-rich carbon isotopes.A few high energy resonances,which also indicate the presence of the σ-bond molecular structure,are observed;however,further studies are still required to clarify their ascription in band systematics.
基金Supported by National Key R&D Program of China(2018YFA0404403)the National Natural Science Foundation of China(11535004,11775004,11405005,11375017)
文摘An experiment for m p（14C},14C＊→10Be＋α）p inelastic excitation and decay was performed in inverse kinematics at a beam energy of 25.3 MeV/u. A series of 14C excited states, including a new one at 18.3（1） MeV, were observed which decay to various states of the final nucleus of 10Be. A specially designed telescope system, installed around zero degrees, played an essential role in detecting the resonant states near the α-separation threshold. A state at 14.1（1） MeV is clearly identified, being consistent with the predicted band-head of the molecular rotational band characterized by the π-bond linear chain configuration. Further clarification of the properties of this exotic state is suggested by using appropriate reaction tools.
基金Supported by the the National Key R&D Program of China(2018YFA0404403)the National Natural Science Foundation of China(11535004,11775013,11875074,11875073)
文摘In order to describe charge exchange reactions at intermediate energies,we implemented as a first step the formulation of the normal eikonal approach.The calculated differential cross-sections based on this approach deviated significantly from the conventional DWBA calculations for CE reactions at 140 MeV/nucleon.Thereafter,improvements were made in the application of the eikonal approximation so as to keep a strict three-dimensional form factor.The results obtained with the improved eikonal approach are in good agreement with the DWBA calculations and with the experimental data.Since the improved eikonal approach can be formulated in a microscopic way,it is easy to apply to CE reactions at higher energies,where the phenomenological DWBA is a priori difficult to use due to the lack,in most cases,of the required phenomenological potentials.
基金Supported by the National Key R&D Program of China (2018YFA0404403)the National Natural Science Foundation of China (11875074, 11875073, 12027809,11961141003, U1967201, 11775004, and 11775003)+1 种基金the Continuous Basic Scientific Research Project (WDJC-2019-13)the State Key Laboratory of Nuclear Physics and Technology,Peking University (NPT2020KFY10)。
文摘A transfer reaction and cluster-decay experiment,12C(16O,24Mg→ α+20Ne)α, was performed at a beam energy of 96 MeV. Both recoil and decay α particles were detected in coincidence, allowing us to deduce the energymomentum of a20Ne fragment. A number of resonant states of24Mg were reconstructed up to an excitation energy of approximately 30 MeV. Owing to the experimentally achieved excellent resolutions of the Q-value and excitationenergy spectra, the relative decay widths for each resonant state in24Mg to various final states of20Ne were extracted, along with the total decay width. The obtained results provide good testing ground for theoretical descriptions of multiple clustering configurations in24Mg.
