Isomer spectroscopy in (216)(90)Th(126) and the magicity of (218)(92)U(126)

Excited states in (216)Th were investigated via prompt and delayed gamma decays and the recoil-decay tagging method. The decay schemes of the I(pi) = (8+), t(1/2) = 128(8) micros, the I(pi) = (11-), t(1/2) = 615(55) ns, and the I(pi) = (14+), t(1/2) > or = 130 ns isomers were established. The configuration pi h(9/2)f(7/2) is assigned to the I(pi) = (8+) isomer, which implies that the h(9/2) and f(7/2) states are nearly degenerate. This is ascribed to increased binding of the f(7/2) orbital by its coupling to a low-lying I(pi) = (3-) state at E(x) = 1687 keV. The role of octupole and pairing correlations for a Z = 92 shell closure prediction is discussed on the basis of shell model calculations.     

On the structure of low-lying levels in 56Ni

It is shown possible to understand the structure of the low-lying states in the nucleus ⁵⁶Ni, in a simple way, in terms of the Hartree-Fock intrinsic states resulting from the Kuo-Brown effective interaction for the 2p-1f shell, modified slightly so as to satisfy certain constraints imposed on it by the B(E2) (0 → 2) systematics in the shell.     

Reduction of the spin-orbit splittings at the n = 28 shell closure

The N = 28 shell closure has been investigated via the 46Ar(d,p)47Ar transfer reaction in inverse kinematics. Energies and spectroscopic factors of the neutron p(3/2), p(1/2), and f(5/2) states in 47Ar were determined and compared to those of the 49Ca isotone. We deduced a reduction of the N = 28 gap by 330(90) keV and spin-orbit weakenings of approximately 10(2) and 45(10)% for the f and p states, respectively. Such large variations for the f and p spin-orbit splittings could be accounted for by the proton-neutron tensor force and by the density dependence of the spin-orbit interaction, respectively. This contrasts with the picture of the spin-orbit interaction as a surface term only.     

Torsional Splitting in the Degenerate Vibrational States of (70)Ge(2)H(6): Rotation-Torsion Analysis of the nu(7) and nu(9) Fundamentals

The rotational and torsional structure of the nu(7) and nu(9) degenerate fundamentals of (70)Ge(2)H(6) has been analyzed under high resolution. The torsional structure of both v(7) = 1 and v(9) = 1 states can be fitted by a simple one-parameter formula. The x,y-Coriolis interaction with the parallel nu(5) fundamental was accounted for in the analysis of nu(7). A strong perturbation of the J structure of the E(3s) torsional component of the KDeltaK = -2 subbranches of nu(9) can be explained by the resonance with an E(3s) excited level of the pure torsional manifold. The perturber is centered at 361.58 cm(-1), very close to the value estimated with a barrier height of 285 cm(-1). This confirms that the fundamental torsional wavenumber is close to 103 cm(-1), in good agreement with the "ab initio" prediction. The torsional splittings of all the infrared active degenerate fundamentals, nu(7), nu(8), and nu(9), follow the trend predicted by theory, and have been fitted by exploratory calculations accounting only for the torsional Coriolis-coupling mechanism of all degenerate vibrational fundamentals in several torsional states. This confirms that torsional Coriolis coupling is the dominant mechanism responsible for the decrease of the torsional splitting in the degenerate vibrational states. A higher value of the barrier had to be used for the nu(9) mode. Copyright 2000 Academic Press.     

Is the nuclear spin-orbit interaction changing with neutron excess?

The difference in the energies of the lowest states corresponding to the two nodeless single-particle orbitals outside the Z=50 closed proton shell, h(11/2) and g(7/2), increases with neutron excess. We have measured the Sn(alpha,t) reaction for all seven stable even Sn isotopes and found that the spectroscopic factors are constant for these two states, confirming their characterization as single-particle states. The trend in energies is consistent with a decrease in the nuclear spin-orbit interaction. A similar trend, also suggesting a decreasing spin-orbit splitting, is seen in the energies of the neutron single-particle states outside the N=82 core, i(13/2) and h(9/2).     

Dy3+激活无水芒硝在真空紫外光激发下的发光性质

在空气中900℃温度下,将纯天然无水芒硝( Na2 SO4)和DyF3的混合粉末加热25 min,制备了Na2SO4:Dy3+新型发光材料.通过同步辐射研究了NaSO4:Dy3+的发光性质.并测量了在室温中真空紫外-紫外光下的发射和激发光谱.根据发射光谱得到了不同Dy3+掺杂浓度和不同激发下发光的黄蓝比(Y/B)是不同的.通过监测黄色发光得到的激发光谱,分别由Dy3+,4f9→4f85d跃迁(172 nm)、O2--Tm3+之间的电荷转移带(165 nm)引起的强激发谱和基质吸收(138,245 nm)、对应Dy3+,6 H15/2→4 D7/2,6H15/2→6 P3/2,6 H15/2→6P7/2跃迁(299,325,351nm)引起的弱激发谱组成.     

Eu原子4f~76p_(3/2)ns自电离态的光谱的研究(英文)

采用孤立实激发技术,对铕原子4f~76p_(3/2)ns(n=7,8)自电离态的光谱进行了系统的研究,同时是首次在不同激光偏振组合下进行的研究。首先,用前两束激光分步将铕原子从基态4f~76s~2经中间4f~76s6p态激发至4f~76sns里德堡态,然后再用第三束激光通过离子实4f~76s~+→4f~76p~+_(3/2)的跃迁将其进一步激发至4f~76p_(3/2)7s自电离态或4f~76p_(3/2)8s自电离态。对铕原子4f~76p_(3/2)ns(n=7,8)自电离态复杂的光谱分别给出了详细的解释,从中我们可以获得一些重要的光谱信息,比如自电峰的能级位置和线宽等,同时还可以观察到收敛于不同离子限的自电离系列之间的组态相互作用。最后,通过比较不同激光偏振组合下的自电离光谱,确定了一些自电离态的总角动量的值。     

粒子-转子模型和推转壳模型中的能谱统计分析

用粒子–转子模型和推转壳模型研究了6个粒子分别填充在单j壳和双j壳上的混沌行为.分析了单j壳和双j壳情况下能谱的最近邻能级间距分布和谱刚度随自旋及推转频率的变化,结果表明,当组态空间大小不变时,系统在双j壳(g_7/2+d_5/2)情况下比在单j壳(i_13/2)情况下更规则,而当组态空间从单j壳(i_13/2)扩大到双j壳(i_13/2+g_9/2)时,系统的混沌程度变化不大.同时比较了将6个粒子的两体相互作用分别取为δ力和对力时的系统的混沌行为     

Magnetic excitations in EuCu(2)(Si(x)Ge(1-x))(2): from mixed valence towards magnetism

We report the inelastic neutron scattering study of spin dynamics in EuCu(2)(Si(x)Ge(1-x))(2) (x?=?1, 0.9, 0.75, 0.6), performed in a wide temperature range. At x?=?1 the magnetic excitation spectrum was found to be represented by the double-peak structure well below the energy range of the Eu(3+) spin-orbit (SO) excitation (7)F(0)→(7)F(1), so that at least the high-energy spectral component can be assigned to the renormalized SO transition. Change of the Eu valence towards 2?+ with increased temperature and/or Ge concentration results in further renormalization (lowering the energy) and gradual suppression of both inelastic peaks in the spectrum, along with developing sizeable quasielastic signal. The origin of the spectral structure and its evolution is discussed in terms of excitonic model for the mixed valence state.     

Hartree-Fock-Bogolubov projected spectra for Cr and Fe isotopes and the effective interactions in the 2p-1f shell

The intrinsic states of Cr and Fe isotopes are obtained by carrying out deformed Hartree-Fock-Bogolubov calculations employing the Kuo-Brown effective interaction for the 2p-1f shell modified slightly to satisfy the restrictions imposed on it by the B (E2) (0→2) systematics in the shell. The angular momentum projected spectra resulting from the modified interaction are in good agreement with the experimental results.     

Application of electric field ionization method to detect the high-lying Rydberg states of Eu I

The 4f~76s(~9S)np 8 P J (J = 5/2, 7/2, 9/2) Rydberg series converging to the first ionization limit 4f 7 6s 9 S 4 of the Eu atom using the three-step laser excitation and electric-field-ionization (EFI) method are studied. First, the Eu atom is excited from the 4f 7 6s 2 8 S o 7/2 ground state to the 4f 7 6s7s 8 S o 7/2 state through the 4f 7 6s6p 10 P 9/2 state by the first two dye lasers. Next, it is populated to many higher-n members of the 4f 7 6s( 9 S)np 8 P J Rydberg series by the third dye laser whose wavelength is scanned within a certain range. Finally, the atom in these higher-n states is ionized by the external pulsed electric field. With the field strength up to 2 kV/cm, we can detect the atom in 4f 7 6s(9 S)np 8 P J states with n 40. With the given laser line width, the level energies of Rydberg states with n as high as 72 can be determined. We not only confirm the previous data on the 4f 7 6s(9 S) np 8 P J Rydberg series, but also extend the n-value assignment significantly by detecting more states.     

High-Resolution Spectroscopy of Jet-Cooled (32)SO(2) and (34)SO(2): The ã(3)B(1)-;X(1)A(1), 2(1)(0) and 1(1)(0) Bands

Laser-induced excitation spectra of the two bands ?(3)B(1)-;X(1)A(1), 2(1)(0) and 1(1)(0) of (32)SO(2) and (34)SO(2) have been recorded in a supersonic jet at a resolution of 0.015 cm(-1). The rotational and electron-spin fine structure has been analyzed for both isotopic species. Analysis of the rotational and electron-spin fine structure yields precise values of the rotational constants A, B, and C and the spin constants alpha and beta for both (32)SO(2) and (34)SO(2) in the states ?(3)B(1) (010) and (100). No interaction between these two vibrational states with any nearby triplet state is observed for rotational levels with J 相似文献   

Large-scale shell model calculations for exotic nuclei

Recent shell model calculations for the neutron-rich nuclei around the magic numbers N = 20, N = 28 and N = 40 are reviewed. We stress two points: i) The crucial role played by the monopole part of the effective interaction that determines the evolution of the spherical mean field. In particular, the reduction in the quasiparticle gaps at the magic numbers can erode or even erase the shell closures. ii) The rich variety of structures that can be found in these situations, with coexisting deformed and spherical states, rapid changes of behaviour with N or Z, and the massive occurrence of intruder states as ground states. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: alfredo.poves@uam.es     

群表示论的物理方法(Ⅴ)——SU3?SO3和SU4?SU2×SU2分类基

本文给出了核物理中常用的SU₃?SO₃(f=1—6)和SU₄?SU₂×SU₂波函数在Gelfand表象中的展开系数。 关键词：     

Hydrogen on W (100): Electron stimulated desorption and a structural model

Prompted by the peculiar shape of the curve of election-induced H⁺ current versus coverage for hydrogen on W(100) which has been observed before, we have restudied this system by correlated ESD, thermal desorption, and LEED measurements. The maxima in ESD signal and intensity of the half-order LEED spots, and the appearance of a second desorption peak are roughly correlated at $\text{1}\text{4}$ coverage. Using this observation and the exact shape of the ESD curve, a structural model is derived in which two different, but uniform states (i and f) exist, the first, i, being exclusively occupied up to $\text{1}\text{4}$ monolayer, and the second, f, at saturation. A gradual conversion from i to f takes place at $\text{1}\text{4}\text{< θ < 1}$ which is caused by the interaction between adsorbed H atoms. From this model a differential equation for the occupation numbers of i and f states, respectively, is derived and solved numerically; it yields good agreement with the experimental ESD curve. Discussing the possible physical realization of the two states, it can be made probable that they must exist on two different sites and have fourfold (i) and twofold (f) symmetry, so that the conversion is accompanied by a shift of the binding site of the adatom.     

The Gamow shell model with realistic interactions: a theoretical framework for ab initio nuclear structure at drip-lines

Ab initio approaches are among the most advanced models to solve the nuclear many-body problem. In particular, the no-core–shell model and many-body perturbation theory have been recently extended to the Gamow shell model framework, where the harmonic oscillator basis is replaced by a basis bearing bound, resonance and scattering states, i.e. the Berggren basis. As continuum coupling is included at basis level and as configuration mixing takes care of inter-nucleon correlations, halo and resonance nuclei can be properly described with the Gamow shell model. The development of the no-core Gamow shell model and the introduction of the $\hat{\bar{Q}}$-box method in the Gamow shell model, as well as their first ab initio applications, will be reviewed in this paper. Peculiarities compared to models using harmonic oscillator bases will be shortly described. The current power and limitations of ab initio Gamow shell model will also be discussed, as well as its potential for future applications.     

一些近期发现的同核异能态的壳模型解释

近期,在101In、123,125Ag和218Pa等核中,首次观测到同核异能态。本工作通过原子核壳模型解释In、Ag同位素和$N\!=\!127$同中素中的这些同核异能态及相关的同核异能态背后的物理原因。101-109In这五个奇A核In同位素中,观测到的$1/2^{-}$同核异能态的激发能非常接近。这可以通过引入中子近期,在101In、123,125Ag和218Pa等核中,首次观测到同核异能态。本工作通过原子核壳模型解释In、Ag同位素和$N\!=\!127$同中素中的这些同核异能态及相关的同核异能态背后的物理原因。101-109In这五个奇A核In同位素中,观测到的$1/2^{-}$同核异能态的激发能非常接近。这可以通过引入中子$0g_{7/2}$和$1d_{5/2}$轨道间的很强的组态混合来解释。更进一步分析表明,这些奇A核In同位素中,从$9/2^{+}$基态到$1/2^{-}$同核异能态,一个质子从$1p_{1/2}$轨道激发到$0g_{9/2}$轨道。这一质子组态变化可能引发中子$0g_{7/2}$和$1d_{5/2}$轨道的单粒子能变化。这样一个原子核内的组态依赖的壳演化被称为第二类壳演化。与In同位素类似,123,125Ag的同核异能态被发现是$1/2^{-}$态,对应着一个质子空穴在$1p_{1/2}$轨道。但之前观测到的115,117Ag的$1/2^{-}$态是基态。这意味着质子$1p_{1/2}$轨道和$0g_{9/2}$轨道在$N\!=\!72$附近发生了反转。壳模型分析表明张量力是造成这两个轨道反转的决定性原因。之前观测到的奇奇核$N\!=\!127$同中素210Bi、212At、214Fr和216Ac中,基态是$1^{-}$态,同时存在高自旋的同核异能态。然而,基于$\alpha$衰变性质和壳模型计算,推荐218Pa中的基态和新发现的同核异能态分别为$8^{-}$态和$1^{-}$态。奇奇核$N\!=\!127$同中素基态和同核异能态的演化是由质子中子相互作用从粒子粒子形式转化为空穴粒子形式以及质子组态混合所导致。总的来说,壳模型对这些双幻核100Sn、132Sn和208Pb附近核中新发现的同核异能态有较好的描述。双幻核附近核中的同核异能态,也称为壳模型同核异能态,是核结构研究中非常重要的。因为这些同核异能态常常提供了中重质量区域极端丰中子和缺中子原子核中的第一个谱学性质,并包含了丰富的物理信息,比如质子中子相互作用及其在壳演化中的作用。     

气溶胶生长过程的微观动力学研究

气溶胶作为大气颗粒物的重要成分对大气环境以及人体健康均有重要影响.其中气溶胶的吸湿性作为影响其在大气中存活时间以及物理化学性质的重要因素受到广泛关注.目前对于气溶胶颗粒的吸湿性研究较为简单,对于气溶胶颗粒物微观结构对吸湿性的影响较少.本文根据Langmuir吸附模型、Fick扩散定律建立了单颗粒的气-粒作用模型,分析了气溶胶颗粒物的均匀分布结构(H2O/C2H2O4)以及非均匀分布结构(H2O/C2H2O4/H2SO4)对其吸湿性的不同影响。研究结果发现,气溶胶颗粒物的非均匀分布结构会影响其吸湿过程的快慢;对于理想流体构成的气溶胶分子,由于分子之间不存在分子间相互作用,因此气-粒间的水分子交换更快,颗粒物外侧浓度首先升高,接着在浓度差的作用下,内侧颗粒逐渐向外扩散,直至达到平衡;相较与大尺寸的颗粒,在相同体积比的条件下,小颗粒由于气溶胶颗粒物的接触角大,因此表面张力大,水分更难流失;此外,由于大尺寸的气溶胶颗粒物表面积体积比较小,因此颗粒失水速度低,需要更多的时间达到相平衡。     

一维硫酸镉-双咪唑配合物的合成、结构及谱学性质研究

采用水热合成的方法,得到一种新颖镉的配合物{[Cd(H2biim)2(SO4)].3H2O}n(1,H2biim=2,2’-biimidazole)。通过X-ray单晶衍射分析可知,在该化合物中,SO24-桥连Cd(Ⅱ)离子在c轴上形成"之"字形一维无机CdSO4链。双咪唑配体通过与镉的配位作为支链悬挂在链的两侧,链与链之间分别通过π—π堆积和氢键作用,拓展为三维超分子网络。二维红外相关光谱分析表明SO24-的对称伸缩振动及咪唑环上的N—C伸缩和反伸缩振动,以及NC伸缩振动对热微扰均有响应。稳态荧光分析显示,配合物在397nm光激发下,在498nm处出现了强的蓝光,该发射带归属为配体到金属的荷移跃迁。