In this study,we investigate the robustness of pair structures for nuclear yrast states,that is,whether the structures of relevant collective pairs as building blocks of different yrast states are the same.We focus on...In this study,we investigate the robustness of pair structures for nuclear yrast states,that is,whether the structures of relevant collective pairs as building blocks of different yrast states are the same.We focus on deformed and transitional nuclei and study the yrast states of^(28)Si,^(50)Cr,and^(132)Xe,whose experimental R_(4/2)values are 2.60,2.40,and 2.16,respectively,using the nucleon-pair approximation(NPA)and shell-model effective interactions.For each yrast state,we consider optimized pair structures to be those providing the energy minimum for this state.To find the minimum,many full NPA calculations are performed with varying pair structures,and the numerical optimization procedure of the conjugate gradient method is implemented.Our results suggest that optimized pair structures remain the same for all states within a rotational band of a deformed nucleus.Our results also suggest that after backbending,that is,changing of the intrinsic state,the structure of the S pair,which is essential to build the monopole pairing correlation,remains approximately unchanged,whereas the structures of the non-S pairs,which are essential to build the quadrupole correlation,change significantly.展开更多
Experimentally observed superdeformed(SD) rotational bands in36Ar and40Ar are studied by the cranked shell model(CSM) with the pairing correlations treated by a particle-number-conserving(PNC) method.This is the first...Experimentally observed superdeformed(SD) rotational bands in36Ar and40Ar are studied by the cranked shell model(CSM) with the pairing correlations treated by a particle-number-conserving(PNC) method.This is the first time that PNC-CSM calculations have been performed on the light nuclear mass region around A=40.The experimental kinematic moments of inertia J~((1))versus rotational frequency are reproduced well. The backbending of the SD band at frequency around ω =1.5 Me V in36Ar is attributed to the sharp rise of the simultaneous alignments of the neutron and proton 1 d5/2[202]5/2 pairs and 1 f7/2[321]3/2 pairs, which is a consequence of the band crossing between the 1 d5/2[202]5/2 and 1 f7/2[321]3/2 configuration states. The gentle upbending at low frequency of the SD band in40Ar is mainly affected by the alignments of the neutron 1 f7/2[321]3/2 pairs and proton 1 d5/2[202]5/2 pairs.The PNC-CSM calculations show that besides the diagonal parts, the off-diagonal parts of the alignments play an important role in the rotational behavior of the SD bands.展开更多
In the present work the nuclear structure properties and the backbending phenomena of even-even isotopes at A ≈ 70 mass region are analyzed using two simultaneous theoretical models based on a simple modified version...In the present work the nuclear structure properties and the backbending phenomena of even-even isotopes at A ≈ 70 mass region are analyzed using two simultaneous theoretical models based on a simple modified version of the collective model predictions besides an improved version of exponential model with the inclusion of pairing correlation. In general, both models successfully describe the backbending phenomena in that region. From the comparison between the predictions of the two proposed models a firm conclusion is obtained concerning the superiority of the simple improved version of the exponential model in describing the forward and down-bending region of the φ-ω<sup>2</sup> plots.展开更多
The microscopic mechanism of nine experimentally observed bands in ^178W is investigated using the particle-number conserving method of the cranked shell model with monopole and quadrupole paring interactions. The exp...The microscopic mechanism of nine experimentally observed bands in ^178W is investigated using the particle-number conserving method of the cranked shell model with monopole and quadrupole paring interactions. The experimental results, including the moments of inertia and angular momentum alignments of nine bands in ^178W, are reproduced well by the particle-number conserving calculations, in which no free parameter is involved. Calculations demonstrate that occurrence of sharp backbending comes mainly from the contribution of high-j intruder orbitals vi13/2 or πh11/2 and their interference effect with orbitals near the Fermi surface. Theω variation of the occupation probability of each cranked orbital and the contribution to moment of inertia from each cranked orbital are analyzed.展开更多
通过熔合蒸发反应^(181)Ta(^(16)O,5n)^(192)Tl,在入射束流为97 Me V能量下,布居^(192)Tl的高自旋态,更新了^(192)Tl的能级纲图。共增加8条新能级,尝试性地指定了能级自旋,将负宇称晕带的能级推高到23-。讨论了^(192)Tl与相邻同位素奇奇...通过熔合蒸发反应^(181)Ta(^(16)O,5n)^(192)Tl,在入射束流为97 Me V能量下,布居^(192)Tl的高自旋态,更新了^(192)Tl的能级纲图。共增加8条新能级,尝试性地指定了能级自旋,将负宇称晕带的能级推高到23-。讨论了^(192)Tl与相邻同位素奇奇核^(194,196,198)Tl负宇称晕带的旋称劈裂与反转现象,发现随着中子数增加,^(196,198)Tl在高自旋处出现了旋称反转,其原因可能是由于中子质子相互作用与科里奥利力相互竞争所致。展开更多
基金Supported by the National Natural Science Foundation of China(11875134,11875188,12175071,11975151,11961141003)the Shanghai Key Laboratory of Particle Physics and Cosmology(21DZ2271500-2)。
文摘In this study,we investigate the robustness of pair structures for nuclear yrast states,that is,whether the structures of relevant collective pairs as building blocks of different yrast states are the same.We focus on deformed and transitional nuclei and study the yrast states of^(28)Si,^(50)Cr,and^(132)Xe,whose experimental R_(4/2)values are 2.60,2.40,and 2.16,respectively,using the nucleon-pair approximation(NPA)and shell-model effective interactions.For each yrast state,we consider optimized pair structures to be those providing the energy minimum for this state.To find the minimum,many full NPA calculations are performed with varying pair structures,and the numerical optimization procedure of the conjugate gradient method is implemented.Our results suggest that optimized pair structures remain the same for all states within a rotational band of a deformed nucleus.Our results also suggest that after backbending,that is,changing of the intrinsic state,the structure of the S pair,which is essential to build the monopole pairing correlation,remains approximately unchanged,whereas the structures of the non-S pairs,which are essential to build the quadrupole correlation,change significantly.
基金Supported by National Natural Science Foundation of China(11775112 and 11275098)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Experimentally observed superdeformed(SD) rotational bands in36Ar and40Ar are studied by the cranked shell model(CSM) with the pairing correlations treated by a particle-number-conserving(PNC) method.This is the first time that PNC-CSM calculations have been performed on the light nuclear mass region around A=40.The experimental kinematic moments of inertia J~((1))versus rotational frequency are reproduced well. The backbending of the SD band at frequency around ω =1.5 Me V in36Ar is attributed to the sharp rise of the simultaneous alignments of the neutron and proton 1 d5/2[202]5/2 pairs and 1 f7/2[321]3/2 pairs, which is a consequence of the band crossing between the 1 d5/2[202]5/2 and 1 f7/2[321]3/2 configuration states. The gentle upbending at low frequency of the SD band in40Ar is mainly affected by the alignments of the neutron 1 f7/2[321]3/2 pairs and proton 1 d5/2[202]5/2 pairs.The PNC-CSM calculations show that besides the diagonal parts, the off-diagonal parts of the alignments play an important role in the rotational behavior of the SD bands.
文摘In the present work the nuclear structure properties and the backbending phenomena of even-even isotopes at A ≈ 70 mass region are analyzed using two simultaneous theoretical models based on a simple modified version of the collective model predictions besides an improved version of exponential model with the inclusion of pairing correlation. In general, both models successfully describe the backbending phenomena in that region. From the comparison between the predictions of the two proposed models a firm conclusion is obtained concerning the superiority of the simple improved version of the exponential model in describing the forward and down-bending region of the φ-ω<sup>2</sup> plots.
基金National Natural Science Foundation of China under Grant No.10675006
文摘The microscopic mechanism of nine experimentally observed bands in ^178W is investigated using the particle-number conserving method of the cranked shell model with monopole and quadrupole paring interactions. The experimental results, including the moments of inertia and angular momentum alignments of nine bands in ^178W, are reproduced well by the particle-number conserving calculations, in which no free parameter is involved. Calculations demonstrate that occurrence of sharp backbending comes mainly from the contribution of high-j intruder orbitals vi13/2 or πh11/2 and their interference effect with orbitals near the Fermi surface. Theω variation of the occupation probability of each cranked orbital and the contribution to moment of inertia from each cranked orbital are analyzed.
文摘通过熔合蒸发反应^(181)Ta(^(16)O,5n)^(192)Tl,在入射束流为97 Me V能量下,布居^(192)Tl的高自旋态,更新了^(192)Tl的能级纲图。共增加8条新能级,尝试性地指定了能级自旋,将负宇称晕带的能级推高到23-。讨论了^(192)Tl与相邻同位素奇奇核^(194,196,198)Tl负宇称晕带的旋称劈裂与反转现象,发现随着中子数增加,^(196,198)Tl在高自旋处出现了旋称反转,其原因可能是由于中子质子相互作用与科里奥利力相互竞争所致。
