By adopting different neutron and proton density distributions,cluster decay half-lives were investigated using double-folding potentials with constant and nuclear asymmetry dependent sets of nuclear density parameter...By adopting different neutron and proton density distributions,cluster decay half-lives were investigated using double-folding potentials with constant and nuclear asymmetry dependent sets of nuclear density parameters.Two adopted asymmetry dependent sets of parameters were fitted based on microscopic calculations,and they were calculated based on the neutron skin/halo-type nuclei assumption and by employing experimental rms charge radii.A bulk agreement between theory and experiment was obtained for all sets of parameters using a calculated cluster preformation probability.Few differences were observed between the skin and halo-type assumptions.However,the notable role of the asymmetry parameter was observed in the relatively large differences between the skin and skintype with zero thickness.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
The exploration of exotic shapes and properties of atomic nuclei,e.g.,αcluster and toroidal shape,is a fascinating field in nuclear physics.To study the decay of these nuclei,a novel detector aimed at detecting multi...The exploration of exotic shapes and properties of atomic nuclei,e.g.,αcluster and toroidal shape,is a fascinating field in nuclear physics.To study the decay of these nuclei,a novel detector aimed at detecting multipleα-particle events was designed and constructed.The detector comprises two layers of double-sided silicon strip detectors(DSSD)and a cesium iodide scintillator array coupled with silicon photomultipliers array as light sensors,which has the advantages of their small size,fast response,and large dynamic range.DSSDs coupled with cesium iodide crystal arrays are used to distinguish multipleαhits.The detector array has a compact and integrated design that can be adapted to different experimental conditions.The detector array was simulated using Geant4,and the excitation energy spectra of someα-clustering nuclei were reconstructed to demonstrate the performance.The simulation results show that the detector array has excellent angular and energy resolutions,enabling effective reconstruction of the nuclear excited state by multipleαparticle events.This detector offers a new and powerful tool for nuclear physics experiments and has the potential to discover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms.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
We examine the structural properties and half-life decay of Ra isotopes within the axially deformed Relativistic Mean-Field（RMF）theory with NL3 force parameters.We work out the binding energy（BE）,RMS radii,two-neu...We examine the structural properties and half-life decay of Ra isotopes within the axially deformed Relativistic Mean-Field（RMF）theory with NL3 force parameters.We work out the binding energy（BE）,RMS radii,two-neutron separation energies（S（2n））,and some other observables.The results are in good agreement with the finite-range droplet model（FRDM）and experimental results.Considering the possibility of neutron magic number,theα-decay and cluster decay half-lives of Ra isotopes are calculated systematically using the Q-values obtained from the RMF formalism.These decay half-life calculations are carried out by taking three different empirical formulae.The calculated decay half-lives are found to be highly sensitive to the choice of Q-values.Possible shell or sub-shell closures are found at daughter nuclei with N=128 and N=126 when alpha and 8Be,12C,18O respectively are emitted from Ra isotopes.Though the cluster radioactivity is affected by the shell closure of parent and daughter,a long half-life indicates the stability of the parent,and a small parent half-life indicates that the shell stability of the daughter against decay.展开更多
Two-proton emissions from the excited states of 17,18Ne,28P and 28,29S were investigated experimentally by the radioactive beams bombarding on the 197Au target via the Coulomb excitation.The complete-kinematics measur...Two-proton emissions from the excited states of 17,18Ne,28P and 28,29S were investigated experimentally by the radioactive beams bombarding on the 197Au target via the Coulomb excitation.The complete-kinematics measurements were actualized by the stacks of silicon-strip detectors and CsI+PIN array detectors.The invariant mass of final systems as well as the relative momentum,opening angle,and relative energy of the two emitted protons was reconstructed under the framework of relativ istic kinematics.Visible proton-proton correlations were observed in these systems.The mechanisms of two-proton emission were analyzed in a simple schematic model,in which the extreme decay modes like He cluster emission,three-body 2 phase-space decay,and two-body sequential decay were taken into account.With the help of Monte-Carlo simulations,the two protons emitted from the 6.15 MeV excited state of Ne and the excited states in the energy region of 9.6–10.4 MeV of S,1829 respectively,exhibited prominent features of2 He cluster decay while for the other cases,no obvious diproton emissions were observed.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
We investigate the formation distance(R0)from the center of the radioactive parent nucleus at which the emitted cluster is most probably formed.The calculations are performed microscopically starting with the solution...We investigate the formation distance(R0)from the center of the radioactive parent nucleus at which the emitted cluster is most probably formed.The calculations are performed microscopically starting with the solution to the time-independent Schr?dinger wave equation for the cluster-core system,using nuclear potentials based on the Skyrme-SLy4 nucleon-nucleon interactions and folding Coulomb potential,to determine the incident and transmitted wave functions of the system.Our results show that the emitted cluster is mostly formed in the pre-surface region of the nucleus,under the effect of Pauli blocking from the saturated core density.The deeperα-formation distance inside the nucleus allows less preformation probability and indicates a more stable nucleus for a longer half-life.Furthermore,theα-particle tends to be formed at a slightly deeper region inside the nuclei,with larger isospin asymmetry,and in the closed shell nuclei.Regarding the heavy clusters,we observed that the formation distance of the emitted clusters heavier thanα-particle increased via increasing the isospin asymmetry of the formed cluster rather than by increasing its mass number.The partial half-life of a certain cluster-decay mode increased with increase of either the mass number or the isospin asymmetry of the emitted cluster.展开更多
A transfer-reaction experiment of ~9Be(~9Be,^(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ^(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the obse...A transfer-reaction experiment of ~9Be(~9Be,^(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ^(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the observed high-lying resonant states,reconstructed from theα+~6He and t+~7Li decay channels,agree with the previously reported results.In addition,two new resonances at 15.6 and 18.8 Me V are identified from the present measurement.The 18.55 Me V state is found to decay into both the t + ~7Lig:s: and t + ~7Li?(0.478 MeV) channels, with a relative branching ratio of 0:93 ± 0:33. Further theoretical investigations are encouraged to interpret this new information on cluster structure in neutron-rich light nuclei.展开更多
文摘By adopting different neutron and proton density distributions,cluster decay half-lives were investigated using double-folding potentials with constant and nuclear asymmetry dependent sets of nuclear density parameters.Two adopted asymmetry dependent sets of parameters were fitted based on microscopic calculations,and they were calculated based on the neutron skin/halo-type nuclei assumption and by employing experimental rms charge radii.A bulk agreement between theory and experiment was obtained for all sets of parameters using a calculated cluster preformation probability.Few differences were observed between the skin and halo-type assumptions.However,the notable role of the asymmetry parameter was observed in the relatively large differences between the skin and skintype with zero thickness.
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.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB34030000)the National Key Research and Development Program of China(No.2022YFA1602404)+1 种基金National Natural Science Foundation(Nos.U1832129 and 11975210)Youth Innovation Promotion Association CAS(No.2017309)。
文摘The exploration of exotic shapes and properties of atomic nuclei,e.g.,αcluster and toroidal shape,is a fascinating field in nuclear physics.To study the decay of these nuclei,a novel detector aimed at detecting multipleα-particle events was designed and constructed.The detector comprises two layers of double-sided silicon strip detectors(DSSD)and a cesium iodide scintillator array coupled with silicon photomultipliers array as light sensors,which has the advantages of their small size,fast response,and large dynamic range.DSSDs coupled with cesium iodide crystal arrays are used to distinguish multipleαhits.The detector array has a compact and integrated design that can be adapted to different experimental conditions.The detector array was simulated using Geant4,and the excitation energy spectra of someα-clustering nuclei were reconstructed to demonstrate the performance.The simulation results show that the detector array has excellent angular and energy resolutions,enabling effective reconstruction of the nuclear excited state by multipleαparticle events.This detector offers a new and powerful tool for nuclear physics experiments and has the potential to discover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms.
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 Project No.SR/FTP/PS-106/2013,SERB,DST,Govt.of India
文摘We examine the structural properties and half-life decay of Ra isotopes within the axially deformed Relativistic Mean-Field（RMF）theory with NL3 force parameters.We work out the binding energy（BE）,RMS radii,two-neutron separation energies（S（2n））,and some other observables.The results are in good agreement with the finite-range droplet model（FRDM）and experimental results.Considering the possibility of neutron magic number,theα-decay and cluster decay half-lives of Ra isotopes are calculated systematically using the Q-values obtained from the RMF formalism.These decay half-life calculations are carried out by taking three different empirical formulae.The calculated decay half-lives are found to be highly sensitive to the choice of Q-values.Possible shell or sub-shell closures are found at daughter nuclei with N=128 and N=126 when alpha and 8Be,12C,18O respectively are emitted from Ra isotopes.Though the cluster radioactivity is affected by the shell closure of parent and daughter,a long half-life indicates the stability of the parent,and a small parent half-life indicates that the shell stability of the daughter against decay.
基金supported by the National Natural Science Foundation of China(Grant Nos.10675169,10735100,and 10727505)the Major State Basic Research Developing Program(Grant No.2007CB815003)
文摘Two-proton emissions from the excited states of 17,18Ne,28P and 28,29S were investigated experimentally by the radioactive beams bombarding on the 197Au target via the Coulomb excitation.The complete-kinematics measurements were actualized by the stacks of silicon-strip detectors and CsI+PIN array detectors.The invariant mass of final systems as well as the relative momentum,opening angle,and relative energy of the two emitted protons was reconstructed under the framework of relativ istic kinematics.Visible proton-proton correlations were observed in these systems.The mechanisms of two-proton emission were analyzed in a simple schematic model,in which the extreme decay modes like He cluster emission,three-body 2 phase-space decay,and two-body sequential decay were taken into account.With the help of Monte-Carlo simulations,the two protons emitted from the 6.15 MeV excited state of Ne and the excited states in the energy region of 9.6–10.4 MeV of S,1829 respectively,exhibited prominent features of2 He cluster decay while for the other cases,no obvious diproton emissions were observed.
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.
文摘We investigate the formation distance(R0)from the center of the radioactive parent nucleus at which the emitted cluster is most probably formed.The calculations are performed microscopically starting with the solution to the time-independent Schr?dinger wave equation for the cluster-core system,using nuclear potentials based on the Skyrme-SLy4 nucleon-nucleon interactions and folding Coulomb potential,to determine the incident and transmitted wave functions of the system.Our results show that the emitted cluster is mostly formed in the pre-surface region of the nucleus,under the effect of Pauli blocking from the saturated core density.The deeperα-formation distance inside the nucleus allows less preformation probability and indicates a more stable nucleus for a longer half-life.Furthermore,theα-particle tends to be formed at a slightly deeper region inside the nuclei,with larger isospin asymmetry,and in the closed shell nuclei.Regarding the heavy clusters,we observed that the formation distance of the emitted clusters heavier thanα-particle increased via increasing the isospin asymmetry of the formed cluster rather than by increasing its mass number.The partial half-life of a certain cluster-decay mode increased with increase of either the mass number or the isospin asymmetry of the emitted cluster.
基金supported by the National Basic Research Program of China (Grant No. 2013CB834402)the National Natural Science Foundation of China (Grant Nos. 11535004, 11275011, 11375017, and 11275001)
文摘A transfer-reaction experiment of ~9Be(~9Be,^(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ^(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the observed high-lying resonant states,reconstructed from theα+~6He and t+~7Li decay channels,agree with the previously reported results.In addition,two new resonances at 15.6 and 18.8 Me V are identified from the present measurement.The 18.55 Me V state is found to decay into both the t + ~7Lig:s: and t + ~7Li?(0.478 MeV) channels, with a relative branching ratio of 0:93 ± 0:33. Further theoretical investigations are encouraged to interpret this new information on cluster structure in neutron-rich light nuclei.
