2000 Vol. 24, No. S1
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Abstract:
This paper discusses the new opportunities of nuclear structure and its characteristic of developments towards multi-directions.The revolutionary progresses of major nuclear experimental facilities and techniques are emphasized to be a solid foundation and guaranty for the new opportunities and developments of nuclear structure.
This paper discusses the new opportunities of nuclear structure and its characteristic of developments towards multi-directions.The revolutionary progresses of major nuclear experimental facilities and techniques are emphasized to be a solid foundation and guaranty for the new opportunities and developments of nuclear structure.
Abstract:
The 11C(p,γ)12N reaction is one of the key processes in hot pp chains.We have carried out a measurement of 11C(d,n)12N reaction.The 11C beam was produced with the secondary beam facility GIRAFFE.The angular distribution was measured and used to deduce ANC through DWBA analysis.We are performinga microscopic study to get the astrophysical S-factor of 11C(p,γ)12N reaction from ANC square constant of 3.5±1.5.This result implies that the direct contribution to (p,γ) reaction is not negligible.
The 11C(p,γ)12N reaction is one of the key processes in hot pp chains.We have carried out a measurement of 11C(d,n)12N reaction.The 11C beam was produced with the secondary beam facility GIRAFFE.The angular distribution was measured and used to deduce ANC through DWBA analysis.We are performinga microscopic study to get the astrophysical S-factor of 11C(p,γ)12N reaction from ANC square constant of 3.5±1.5.This result implies that the direct contribution to (p,γ) reaction is not negligible.
Abstract:
A new rotational band has been observed in )167Lu by 152Sm(19F,4n)167Lu reaction.The high spin transition energier of the new band are almost identical to the triaxial superdeformed bands recently discovered in 163Lu and 165Lu.This new band and the [660] band 171Ta are assigned as triaxical superdeformed bands by total routhian surface calculations based on cranked shell model.The formation mechanism of the superdeformed triaxial band in this region is discussed.
A new rotational band has been observed in )167Lu by 152Sm(19F,4n)167Lu reaction.The high spin transition energier of the new band are almost identical to the triaxial superdeformed bands recently discovered in 163Lu and 165Lu.This new band and the [660] band 171Ta are assigned as triaxical superdeformed bands by total routhian surface calculations based on cranked shell model.The formation mechanism of the superdeformed triaxial band in this region is discussed.
Abstract:
Recent progressof research on high spin states in nuclear group of Tsinghua University has been reviewed.There are two parts in the content:research on octupole deformation of neutron rich odd-A 143,145Ba and 145,147La nuclei by measuring the prompt γ-rays emitted in the spontaneous fission of 252Cf and research on the high spin states of 134,137,138Ce and 122Ba in A=130 neutron-deficient region,which shows the characteristics of shape driving,the shape coexistence,the octupole correlations and the band cross.
Recent progressof research on high spin states in nuclear group of Tsinghua University has been reviewed.There are two parts in the content:research on octupole deformation of neutron rich odd-A 143,145Ba and 145,147La nuclei by measuring the prompt γ-rays emitted in the spontaneous fission of 252Cf and research on the high spin states of 134,137,138Ce and 122Ba in A=130 neutron-deficient region,which shows the characteristics of shape driving,the shape coexistence,the octupole correlations and the band cross.
Abstract:
In recent years,high-spin states in a series of deformed odd-odd nuclei 162Lu,170Ta,174Re,176,178,180Ir and 182Au have been studied in corporation with the researchers in the IMP (Institute of Modem Physics,CAS),CIAE (China Institute of Atomic Energy) and JAERI (Japan Atomic Energy Research Institute).The experimental results are reviewed in this report.The interesting phenomenon of low-spin signature inversion in both the πh11/2⊙νi13/2 and πh9/2⊙νi13/2 configurations has been systematically studied and discussed for the nuclei in this mass region.A possible lowspin signature inversion is suggested for the πh13/2⊙νi13/2 structure in 182,184Au and the limited experimental data seem to support such suggestion.The gradual alignment gains with rotation are reported ,for the first time,in the πh11/2⊙νi13/2 bands of odd-odd 178,180Ir.An unexpected smaller band crossing frequency is observed in 178Ir(most probably in the πd5/2⊙νh9/2 configuration).These anomalies may be associated with the configuration-dependent deformations and/or neutron pairing.
Abstract:
A detailed inquiry is made into the causes of which the definitive evidence for the existence of a hyperdeformed shape in rare earth nuclei has not been found.For the hyperdeformations in the actinide nuclei,the theoretical predictions,experimental methods,primary results and existing problems have been discussed.
A detailed inquiry is made into the causes of which the definitive evidence for the existence of a hyperdeformed shape in rare earth nuclei has not been found.For the hyperdeformations in the actinide nuclei,the theoretical predictions,experimental methods,primary results and existing problems have been discussed.
Abstract:
Five rotational bands with configurations{π7/2+[404]⊙ν5/2+[642]}K=6,{π9/2+[541]⊙ν5/2+[642]}K=7{π1/2+[411]⊙ν5/2+[642]}K=2,{π1/2+[541]⊙ν5/2+[642]}K=2 and {π5/2+[402]⊙ν5/2+[642]}K=5,were populated through the 152Sm(19F,5n)166Lu reaction at a beam energy of 97MeV.The last three bands are identified in the present study.A phase change of level staggering is observed and low spin signature inversion is suggested in the band {π1/2－[541]⊙ν5/2+[642]}K=2.The inversion spin 17.5h (spin at inversion point)of this band fits well to the systematic variation trend of inversion spin,increasing with N and decreasing with Z,for the known π1/2－[541]⊙νi13/2 bands observed in odd-odd deformed nuclei around A=170.
Five rotational bands with configurations{π7/2+[404]⊙ν5/2+[642]}K=6,{π9/2+[541]⊙ν5/2+[642]}K=7{π1/2+[411]⊙ν5/2+[642]}K=2,{π1/2+[541]⊙ν5/2+[642]}K=2 and {π5/2+[402]⊙ν5/2+[642]}K=5,were populated through the 152Sm(19F,5n)166Lu reaction at a beam energy of 97MeV.The last three bands are identified in the present study.A phase change of level staggering is observed and low spin signature inversion is suggested in the band {π1/2－[541]⊙ν5/2+[642]}K=2.The inversion spin 17.5h (spin at inversion point)of this band fits well to the systematic variation trend of inversion spin,increasing with N and decreasing with Z,for the known π1/2－[541]⊙νi13/2 bands observed in odd-odd deformed nuclei around A=170.
Abstract:
Some new development in nuclear structure studies are reviewed briefly.Nuclear supersymmetry put forward in 1980 has been tested in odd-odd nucleus in 1999.In nuclear algebraic models,the problem of reduction in collectivity has been solved.There have been extensive analytic formulas for eletromagnetic transitions in octupole vibration in algebraic model,and they are convenient in analysing nuclear data.It is found that 158Gd is the best experimental example for octupole vibration so far.In nuclear shell model,Monto Carlo shell model and projected shell model have made considerable advancement.Finally,an outlook for nuclear structure in 21st century is made briefly.
Some new development in nuclear structure studies are reviewed briefly.Nuclear supersymmetry put forward in 1980 has been tested in odd-odd nucleus in 1999.In nuclear algebraic models,the problem of reduction in collectivity has been solved.There have been extensive analytic formulas for eletromagnetic transitions in octupole vibration in algebraic model,and they are convenient in analysing nuclear data.It is found that 158Gd is the best experimental example for octupole vibration so far.In nuclear shell model,Monto Carlo shell model and projected shell model have made considerable advancement.Finally,an outlook for nuclear structure in 21st century is made briefly.
Abstract:
Using particle-rotor model,the γ transition energies,signature splitting and M1 transitions for the yrast superdeformed band in odd-A Tl isotopes are investigated and compared with the experimental data.The small difference in the moments of inertia and signature splitting when going from the heavier Tl isotope to lighter ones is thought to reflect the gradual decrease of the quadrupole deformation.The (gKgR)K/Q0 values enable us to confirm that the 81st proton occupies the [642 5/2]orbital.
Using particle-rotor model,the γ transition energies,signature splitting and M1 transitions for the yrast superdeformed band in odd-A Tl isotopes are investigated and compared with the experimental data.The small difference in the moments of inertia and signature splitting when going from the heavier Tl isotope to lighter ones is thought to reflect the gradual decrease of the quadrupole deformation.The (gKgR)K/Q0 values enable us to confirm that the 81st proton occupies the [642 5/2]orbital.
Abstract:
Status of the investigation on superdeformed nuclear bands are surveyed briefly.An algebraic model which can describe the ΔI=4 bifurcation and the identical bands is proposed.The calculated results indicate that the ΔI=4 bifurcation may come from the perturbation holding the SO(5)(or SU(5)) symmetry.Meanwhile the identical bands result from that the mean field for the superdeformed bands to build upon may possess supersymmetry.
Status of the investigation on superdeformed nuclear bands are surveyed briefly.An algebraic model which can describe the ΔI=4 bifurcation and the identical bands is proposed.The calculated results indicate that the ΔI=4 bifurcation may come from the perturbation holding the SO(5)(or SU(5)) symmetry.Meanwhile the identical bands result from that the mean field for the superdeformed bands to build upon may possess supersymmetry.
Abstract:
The framework of the Reflection Asymmetric Shell Model (RASM) used to describe the high-spin states of octupole-deformed nuclei has been formulated by the variational procedure.Some basic features of the Yrast octupole bands can been explained by this model.We calculated the even-even222—228Ra isotopes,the agreement between the theory and the experimental data is good.
The framework of the Reflection Asymmetric Shell Model (RASM) used to describe the high-spin states of octupole-deformed nuclei has been formulated by the variational procedure.Some basic features of the Yrast octupole bands can been explained by this model.We calculated the even-even222—228Ra isotopes,the agreement between the theory and the experimental data is good.
Abstract:
The formalism for Relativistic Continuum hartree-Bogoliubov (RCHB) theory,which is the extension of the Relativistic Mean Field (RMF) and the Bogoliubov transformation in the coordinate representation,and its application to unstable nuclei are reviewed.As the RCHB formalism allows for the proper description of the coupling between the bound state and the continuum by the pairing force,it is suitable not only for stable nuclei but also the nuclei near the drip line.The pairing correlations are taken into account by both a density-dependent force of zero range and the finite range Gogny force.
The formalism for Relativistic Continuum hartree-Bogoliubov (RCHB) theory,which is the extension of the Relativistic Mean Field (RMF) and the Bogoliubov transformation in the coordinate representation,and its application to unstable nuclei are reviewed.As the RCHB formalism allows for the proper description of the coupling between the bound state and the continuum by the pairing force,it is suitable not only for stable nuclei but also the nuclei near the drip line.The pairing correlations are taken into account by both a density-dependent force of zero range and the finite range Gogny force.
Abstract:
The physics aspects of the low density and weakly bound system in the theoretical mean field theory study are presented.The nuclear effective interactions and mean field for nuclei at extreme values of the isospin are focused.
The physics aspects of the low density and weakly bound system in the theoretical mean field theory study are presented.The nuclear effective interactions and mean field for nuclei at extreme values of the isospin are focused.
Abstract:
The equations of state of the neutron star matter are calculated in the relativistic mean-field approximation with different couplings of the hyperons.The properties of neutron stars are studied by solving the Oppenheimer-Vollkoff equation.It shows that these properties change distinctly as different couplings of hyperons are concemed.
The equations of state of the neutron star matter are calculated in the relativistic mean-field approximation with different couplings of the hyperons.The properties of neutron stars are studied by solving the Oppenheimer-Vollkoff equation.It shows that these properties change distinctly as different couplings of hyperons are concemed.
Abstract:
The β-delayed proton precursors 125Nd,128Pm,129Sm,137Gd and 139Dy near the proton dripline were produced by the irradiation of 92Mo,96Ru and 106Cd with an 36Ar beam,and conclusively identified for the first time by using proton-gamma coincidence in combination with a He-jet tape transport system.Their half-lives were determined to be 0.60(15)s,1.0(3)s,0.55(10)s,2.2(2)s and 0.6(2)s,respectively.The measured energy spectra of β-delayed protons and esimated proton branching ratios to the final states in "daughter"nuclei for the precursors 125Nd,129Sm,137Gd and 139Dy,as well as the previously reported ones for the precursors 135Gd and 121Ce,were fitted by a statistical model calculation.The ground-state spins and and parities of 121Ce,125Nd,129Sm,135Gd,137Gd and 139Dy were then assigned as 5/2±,5/2±,1/2+(or 3/2+),5/2±,7/2± and 7/2,respectly.The consistency between the experimental spin-parity assignment and the predicted Nilsson diagrams indirectly indicates that ground states of 121Ce,125Nd,129Sm,135Gd,137Gd and 139Dy are highly deformed with β2～0.3.
The β-delayed proton precursors 125Nd,128Pm,129Sm,137Gd and 139Dy near the proton dripline were produced by the irradiation of 92Mo,96Ru and 106Cd with an 36Ar beam,and conclusively identified for the first time by using proton-gamma coincidence in combination with a He-jet tape transport system.Their half-lives were determined to be 0.60(15)s,1.0(3)s,0.55(10)s,2.2(2)s and 0.6(2)s,respectively.The measured energy spectra of β-delayed protons and esimated proton branching ratios to the final states in "daughter"nuclei for the precursors 125Nd,129Sm,137Gd and 139Dy,as well as the previously reported ones for the precursors 135Gd and 121Ce,were fitted by a statistical model calculation.The ground-state spins and and parities of 121Ce,125Nd,129Sm,135Gd,137Gd and 139Dy were then assigned as 5/2±,5/2±,1/2+(or 3/2+),5/2±,7/2± and 7/2,respectly.The consistency between the experimental spin-parity assignment and the predicted Nilsson diagrams indirectly indicates that ground states of 121Ce,125Nd,129Sm,135Gd,137Gd and 139Dy are highly deformed with β2～0.3.
Abstract:
Using a large-acceptance germanium detector array (Hyperball),the spin-flip M1 γ transition between the ground-state spin doublet of 7ΛLi has been observed.The transition energy is 692±1keV,which provides crucial information on the strength of the spin-spin intetraction between Λ and nucleons.
Using a large-acceptance germanium detector array (Hyperball),the spin-flip M1 γ transition between the ground-state spin doublet of 7ΛLi has been observed.The transition energy is 692±1keV,which provides crucial information on the strength of the spin-spin intetraction between Λ and nucleons.
Abstract:
The experimental research of magnetic rotational band and relative theoretical module were introduced briefly in this paper.Two magnetic rotational bands in 84Rb were reported and discussed.Experimental routhians are given.They are show no signature splitting.The B(M1)/B(E2)ratio was extract for one band.
The experimental research of magnetic rotational band and relative theoretical module were introduced briefly in this paper.Two magnetic rotational bands in 84Rb were reported and discussed.Experimental routhians are given.They are show no signature splitting.The B(M1)/B(E2)ratio was extract for one band.
Abstract:
The structure of a new dibaryon (ΩΩ)0+ is studied and predicted in the framework of the chiral SU(3) quark model by solving a resonating group method equation.The binding energy of this dibaryon is around 100MeV,the mean root square of the distance between two Ωs is 0.84fm and the preliminary estimated mean lifetime is about two times longer than that of the Ω.All these interesting properties and also the two negative charge units it carried could make it be easily identified experimentally in the heavy-ion collision process.
The structure of a new dibaryon (ΩΩ)0+ is studied and predicted in the framework of the chiral SU(3) quark model by solving a resonating group method equation.The binding energy of this dibaryon is around 100MeV,the mean root square of the distance between two Ωs is 0.84fm and the preliminary estimated mean lifetime is about two times longer than that of the Ω.All these interesting properties and also the two negative charge units it carried could make it be easily identified experimentally in the heavy-ion collision process.
Abstract:
The FST model was extended to contain strangeness and then used in mean-field approximation to study the saturation properties and stabilities of the strange hadronic matter containing nucleons,Λ and Ξ hyperons.
The FST model was extended to contain strangeness and then used in mean-field approximation to study the saturation properties and stabilities of the strange hadronic matter containing nucleons,Λ and Ξ hyperons.
Abstract:
Under an Ansatz of density dependence of NNρ coupling,the phase transition of hot nuclear matter for Fumstahl,Serot and Tang's model is investigated.We have found that there is a limit pressure Plim,when P>Plim,the two-phase configuration and the liquid-gas phase transition cannot take place.
Under an Ansatz of density dependence of NNρ coupling,the phase transition of hot nuclear matter for Fumstahl,Serot and Tang's model is investigated.We have found that there is a limit pressure Plim,when P>Plim,the two-phase configuration and the liquid-gas phase transition cannot take place.
Abstract:
Sources of 237Th has been prepared via a multinucleon transfer reaction by 60MeV/u 18O ions bombardment of natural uranium followed by radiochemical separation.The isotope 237Th has been identified.The half-life of 237Th was determined to be (4.69±0.60)min.Not only the new value is in agreement with the earlier one of (5.0±0.9)min obtained in our previous work,but also its experimental precision was improved.
Sources of 237Th has been prepared via a multinucleon transfer reaction by 60MeV/u 18O ions bombardment of natural uranium followed by radiochemical separation.The isotope 237Th has been identified.The half-life of 237Th was determined to be (4.69±0.60)min.Not only the new value is in agreement with the earlier one of (5.0±0.9)min obtained in our previous work,but also its experimental precision was improved.
Abstract:
Nuclear spectroscopic experiment of nuclei with extreme short half-life far from the β stability by using the RIBLL facility has been carried out.The isotope 29S was produced by projectile fragmentation of 69MeV/u 36Ar+17 on natNi with thickness of 92.3mg/cm2.29S ions were separated and implanted in the Si(Au)detectors.Beta-delayed proton radioactivity has been measured for the 29S isotopes.The measured energy spectrum of β-delayed protons and half-lives are in good agreement with literature.The used experimental method was approved to be feasible for the spectroscopic measurements.
Nuclear spectroscopic experiment of nuclei with extreme short half-life far from the β stability by using the RIBLL facility has been carried out.The isotope 29S was produced by projectile fragmentation of 69MeV/u 36Ar+17 on natNi with thickness of 92.3mg/cm2.29S ions were separated and implanted in the Si(Au)detectors.Beta-delayed proton radioactivity has been measured for the 29S isotopes.The measured energy spectrum of β-delayed protons and half-lives are in good agreement with literature.The used experimental method was approved to be feasible for the spectroscopic measurements.
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