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1.
We have performed large-scale shell model calculations of the Gamow-Teller strength distributions in NZ pf -shell nuclei. These calculations were motivated by the experimental attempts to measure the low-lying GT strength for the even-even N = Z + 2 or N = Z - 2 nuclei 46Ti , 50Cr , 54Fe and 62Ge , where a sizable low-energy GT strength could be interpreted as reminiscence of SU(4) symmetry; in the limit of exact SU(4) symmetry the GT- strength would be concentrated in a single transition to the lowest T = 0, J = 1+ state in the daughter. We confirm that the SU(4) symmetry is strongly broken by the spin-orbit interaction and by increasing neutron excess.  相似文献   

2.
The spin polarized β-emitting nuclei 12B (Iπ = 1+, T1/2 = 20.18 ms) were produced by the nuclear reaction 11B(d, p) 12B and by the selection technique of the incident deuteron energy and the 12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei 12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment of 12B was determined to be μ = 0.99993 ± 0.00048 nm or g = 0.99993 ± 0.00048 after the precise correction of the Knight shift.  相似文献   

3.
用原子分子反应静力学原理推导出CrHn(n =0,+1,+2)的电子状态及其离解极限.对H原子采用6-311++G**基组,对Cr原子采用SVP(split valence polarization)全电子基组,用B3PW91方法计算了它们的平衡几何、电子状态,在此基础上分别计算CrH, CrH+的Murrell-Sorbie解析势能函数和CrH2+的解析势能函数及其对应的力常数、光谱参数,理论计算值与实验值和文献计算值符合较好.从离解极限和通道解释了不同的势能函数形状.计算表明:CrH+的势能曲线均具有对应于稳定平衡结构的极小点,说明CrH+可稳定存在.而CrH2+离子的势能曲线对应于不稳定的排斥态,说明CrH2+是不稳定的.  相似文献   

4.
Kota  V K B 《Pramana》1997,48(5):1035-1075
TheU B(6)⊗U F(20) Bose-Fermi dynamical symmetry of interacting boson-fermion model arises when the odd nucleon occupies single particle orbits withj=1/2, 3/2, 5/2, and 7/2. The subgroup structures ofU B(6)⊗U F(20) related to theU B(5) andO B(6) limits of sdIBM (U B(6)) are analysed. Broadly speaking,U B(6)⊗U F(20) admitsU BF(5)⊗U s F (4), SpinBF(5)⊗U k F (5) andU BF(5)⊗U s F (2) limits withU B(5) core and SpinBF(6),O BF(5)⊗U s F (4), SpinBF(6)⊗U k F (5) andO BF(6)⊗U s F (2) limits withO B(6) core respectively. For each of these seven symmetry limits, group chains, quantum numbers labelling the basis states, generators and Casimir operators for the various subgroups and energy formulas are given. Recoupling coefficients (reduced Wigner coefficients) for constructing wavefunctions of low-lying states are tabulated and these will allow (together with sdIBMU B(5) andO B(6) limit results) one to calculateB(E2)’s,B(M1)’s, one and two nucleon transfer strengths etc. in the seven symmetry limits. Experimental examples for theU B(6)⊗U F(20) symmetry limits are briefly discussed.  相似文献   

5.
Ashok Kumar  M R Gunye 《Pramana》1982,19(2):189-202
The equilibrium deformations of tungsten, osmium and platinum nuclei are studied with the self-consistent quadrupole plus pairing interaction model by considering all the nucleons in nucleus explicitly. It is shown that similar results can be obtained by performing calculations with or without the assumption of an inert core. The only difference is in the strength of the quadrupole and pairing interactions to be employed in the respective calculations. The experimental static quadrupole moments and theB (E2) values are correctly reproduced by performing calculations with bare nucleon charge for all the nucleons.  相似文献   

6.
Thesdg interacting boson model (sdgIBM), which includes monopole (s), quadrupole (d) and hexadecupole (g) degrees of freedom, enables one to analyze hexadecupole (E4) properties of atomic nuclei. Various aspects of the model, both analytical and numerical, are reviewed emphasizing the symmetry structures involved. A large number of examples are given to provide understanding and tests, and to demonstrate the predictiveness of thesdg model. Extensions of the model to include proton-neutron degrees of freedom and fermion degrees of freedom (appropriate for odd mass nuclei) are briefly described. A comprehensive account ofsdgIBM analysis of all the existing data on hexadecupole observables (mainly in the rare-earth region) is presented, includingβ 4 (hexadecupole deformation) systematics,B(IS4; 0 GS + →4 γ + ) systematics that give information about hexadecupole component in γ-vibration,E4 matrix elements involving few low-lying 4+ levels,E4 strength distributions and hexadecupole vibrational bands in deformed nuclei. The survey of literature for this review was concluded in December 1991.  相似文献   

7.
The dehydrogenation of CH4 on the Co(1 1 1) surface is studied using density functional theory calculation (DFT). It is found that CH4 is favored to dissociate to CH3 and then transforms to CH2 and CH by sequential dehydrogenation, and CH4 activation into CH3 and H is the rate-determining step on the Co(1 1 1) surface. CH2 is quite unstable on Co(1 1 1) surface. CH dehydrogenation into C and H is difficult. CH3 and H prefer to adsorb on 3-fold hollow hcp and fcc sites, and CH2, CH and C prefer to adsorb on hcp sites.  相似文献   

8.
We discuss a simple approach to enhance sensitivity for (13)C high-resolution solid-state NMR for proteins in microcrystals by reducing (1)H T(1) relaxation times with paramagnetic relaxation reagents. It was shown that (1)H T(1) values can be reduced from 0.4-0.8s to 60-70 ms for ubiquitin and lysozyme in D(2)O in the presence of 10 mM Cu(II)Na(2)EDTA without substantial degradation of the resolution in (13)C CPMAS spectra. Faster signal accumulation using the shorter (1)H T(1) attained by paramagnetic doping provided sensitivity enhancements of 1.4-2.9 for these proteins, reducing the experimental time for a given signal-to-noise ratio by a factor of 2.0-8.4. This approach presented here is likely to be applicable to various other proteins in order to enhance sensitivity in (13)C high-resolution solid-state NMR spectroscopy.  相似文献   

9.
张秀荣  康张李  郭文录 《中国物理 B》2011,20(10):103601-103601
WnC0,± (n=1-6) clusters are investigated by using the density functional theory (DFT) at the B3LYP/LANL2DZ level. We find that the neutral, anionic and cationic ground state structures are similar within the same size, and constituted by substituting a C atom for one W atom in the structures of Wn+1 clusters. The natural bond orbital (NBO) charge analyses indicate that the direction of electron transfer is from the W atom to the 2p orbital of the C atom. In addition, the calculated infrared spectra of the WnC0,± (n=2-6) clusters manifest that the vibrational frequencies of neutral, anionic and cationic clusters are similar in a range of 80 cm-1-864 cm-1. The high frequency, strong peak modes are found to be an almost stretched deformation of the carbide atom. Finally, the polarizabilities of WnC0,± (n=1-6) clusters are also discussed.  相似文献   

10.
The molecular dynamics simulation technique with many-body and semi-empirical potentials is used to calculate the (1 1 4) twin-boundary in gold at different temperatures. Relaxations are found on both sides of the interface with the same magnitude and the phenomenon of coalescence is observed near the interface. The interactions of single-, di- and tri-vacancies with twin-interface at 300 K on mirror and off-mirror sites are calculated. Off-mirror arrangements are favorable for all vacancy clusters, except for the single-vacancy cluster, which is less repulsive on the mirror site. Vacancy clusters energetically prefer to lie at planes closest to the (1 1 4) interface rather than away from it. The effect of temperature on interaction behavior is also calculated.  相似文献   

11.
We calculate the radiative decay widths of the a 0(980) and f 0(980) scalar mesons into ργ and ωγ considering the dynamically generated nature of these scalar resonances within the realm of the chiral unitary approach. The main ingredient in the evaluation of the radiative width of the scalar mesons are the loops coming from the decay into their constituent pseudoscalar-pseudoscalar components and the subsequent radiation of the photon. The dominant diagrams with only pseudoscalar mesons in the loops are found to be convergent while the divergence of those with a vector meson in the loop are written in terms of the two-meson loop function easily regularizable. We provide results for all the possible charge channels and obtain results, with uncertainties, which differ significantly from quark loops models and some version of vector meson dominance.  相似文献   

12.
黄萍  朱正和 《物理学报》2006,55(12):6302-6307
用原子分子反应静力学原理推导出CrHn(n=0,+1,+2)的电子状态及其离解极限. 对H原子采用6-311++G**基组,对Cr原子采用SVP(split valence polarization)全电子基组,用B3PW91方法计算了它们的平衡几何、电子状态,在此基础上分别计算CrH,CrH+的Murrell-Sorbie解析势能函数和CrH2+的解析势能函数及其对应的力常数、光谱参数,理论计算值与实验值和文献计算值符合较好. 从离解极限和通道解释了不同的势能函数形状. 计算表明:CrH+的势能曲线均具有对应于稳定平衡结构的极小点,说明CrH+可稳定存在. 而CrH2+离子的势能曲线对应于不稳定的排斥态,说明CrH2+是不稳定的. 关键词n(n=0')" href="#">CrHn(n=0 +2) 势能函数 光谱参数 稳定性  相似文献   

13.
In this study the adsorption geometry of aspirin molecule on a hydroxylated (0 0 1) α-quartz surface has been investigated using DFT calculations. The optimized adsorption geometry indicates that both, adsorbed molecule and substrate are strongly deformed. Strong hydrogen bonding between aspirin and surface hydroxyls, leads to the breaking of the original hydroxyl–hydroxyl hydrogen bonds (Hydrogenbridges) on the surface. In this case new hydrogen bonds on the hydroxylated (0 0 1) α-quartz surface appear which significantly differ from those at the clean surface. The 1.11 eV adsorption energy reveals that the interaction of aspirin with α-quartz is an exothermic chemical interaction.  相似文献   

14.
陈玉红  张材荣  马军 《物理学报》2006,55(1):171-178
用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G基组水平上对MgmBn(m=1,2;n=1-4)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的振动特性、电离势、成键特性、极化率和超极化率等性质进行了理论研究.结果表明,团簇的最稳定结构大多是平面结构,团簇的稳定结构中通常是几个呈负电性的B原子形成一个负电中心,而其他B原子和Mg原子通常处在端位,且显正电性;团簇中通常是B-B键和B-Mg键共存,极少出现Mg-Mg键, 关键词: mBn(m=1')" href="#">MgmBn(m=1 n=1-4)团簇 密度泛函理论 结构与性质  相似文献   

15.
The crystal structure of [C(NH2)3]2HgBr4 has been determined at room temperature: monoclinic, space group C2/c, with a = 10.035(2), b = 11.164(2), c = 13.358(3) Å, β = 111.67(3)°, and Z = 4. The crystal consists of planar [C(NH2)3]+ and distorted tetrahedral [HgBr4]2? ions. The Hg atom is located on a two-fold axis such that two sets of inequivalent Br atoms exist in an [HgBr4]2? ion. In accordance with the crystal structure, two 81Br NQR lines widely separated in frequency were observed between 77 and ca. 380 K. [C(NH2)3]2HgI4 yielded four 127I NQR lines ascribable to m = ±1/2 ? ±3/2 transitions, indicating that its crystal structure is different from the bromide complex. The 1H NMR T 1 measurements showed a single minimum for the bromide but two minima for the iodide. The analyses based on the C3 reorientations of the planar [C(NH2)3]+ ions gave the activation energies of 29.8 kJ mol?1 for the bromide, and 30.2 and 40.0 kJ mol?1 for the iodide.  相似文献   

16.
The c(4 × 2) structures in (0 0 1) surfaces of Si and Ge have been studied by low-energy electron diffraction (LEED). Using a proper cleaning method for the Si surface, we were able to observe clear c(4 × 2) LEED patterns up to incident energy of ∼400 eV as well as the Ge surface. Extensive experimental intensity-voltage curves allowed us to optimize the asymmetric dimer model up to the eighth layer (including the dimer layer) in depth in the dynamical LEED calculation. Optimized structural parameters are almost the same for the Si and Ge except for the height of the buckled-up atom of the asymmetric dimer. For the Ge surface, the structural parameters are in excellent agreement with those obtained by a previous theoretical calculation. The tilt angle and bond length of the dimer are 18 ± 1 (19 ± 1)° and 2.4 ± 0.1 (2.5 ± 0.1) Å for the Si(0 0 1) (Ge(0 0 1)), respectively.  相似文献   

17.
V2O3(0 0 0 1) films have been grown epitaxially on Au(1 1 1) and W(1 1 0). Under typical UHV conditions these films are terminated by a layer of vanadyl groups as has been shown previously [A.-C. Dupuis, M. Abu Haija, B. Richter, H. Kuhlenbeck, H.-J. Freund, V2O3(0 0 0 1) on Au(1 1 1) and W(1 1 0): growth, termination and electronic structure, Surf. Sci. 539 (2003) 99]. Electron irradiation may remove the oxygen atoms of this layer. H2O adsorption on the vanadyl terminated surface and on the reduced surface has been studied with thermal desorption spectroscopy (TDS), vibrational spectroscopy (IRAS) and electron spectroscopy (XPS) using light from the BESSY II electron storage ring in Berlin. It is shown that water molecules interact only weakly with the vanadyl terminated surface: water is adsorbed molecularly and desorbs below room temperature. On the reduced surface water partially dissociates and forms a layer of hydroxyl groups which may be detected on the surface up to T ∼ 600 K. Below ∼330 K also co-adsorbed molecular water is detected. The water dissociation products desorb as molecular water which means that they recombine before desorption. No sign of surface re-oxidation could be detected after desorption, indicating that the dissociation products desorb completely.  相似文献   

18.
Using scanning tunneling microscopy, growth of In nanoisland arrays on the Si(1 0 0)-c(4 × 12)-Al surface has been studied for In coverage up to 1.1 ML and substrate temperature from room temperature to 150 °C. In comparison to the case of In deposition onto the clean Si(1 0 0) surface or Si(1 0 0)4 × 3-In reconstruction, the In growth mode is changed by the c(4 × 12)-Al reconstruction from the 2D growth to 3D growth, thus displaying a vivid example of the Volmer-Weber growth mode. Possible crystal structure of the grown In nanoislands is discussed.  相似文献   

19.
溴化硼分子及离子的势能函数与垂直电离势   总被引:1,自引:0,他引:1       下载免费PDF全文
为了弄清BBr在金属蚀刻中的机理 ,需了解BBrn(n =0、+ 1、+ 2 )分子及离子体系势能函数和稳定性的信息 ,用原子分子反应静力学原理推导出了BBrn(n =0、+ 1、+ 2 )的基态电子状态及其离解极限 .基于cc pVDZ基组 ,用B3LYP方法计算了他们的平衡几何、电子状态 ,在此基础上分别计算了BBr、BBr+ 的Murrell Sorbie解析势能函数和BBr2 + 的解析势能函数及其对应的力常数、光谱参数 .BBrn(n =+ 1、+ 2 )离子的垂直电离势为 :I+ =9.583 675eV ,I+ + =2 9.3 4 2 3 4eV .计算表明 ,BBr+ 、BBr2 + 的势能曲线均具有对应于稳定平衡结构的极小点 ,说明BBr+ 、BBr2 + 可稳定存在  相似文献   

20.
The spin polarized β-emitting nuclei12B (I π=1+,T 1/2=20.18 ms) were produced by the nuclear reaction11B(d, p)12B and by the selection technique of the incident deuteron energy and the12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment of12B was determined to be μ=0.99993±0.00048 nm org=0.99993±0.00048 after the precise correction of the Knight shift.  相似文献   

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