Observation of Spin Polarized Clock Transition in 87Sr Optical Lattice Clock

Atomic clocks operating at optical frequencies, with much better accuracy compared with microwave atomic clocks, have been assumed to be the next- generation time and frequency standards, Many applications will benefit from this lower frequency un- certainty of optical clocks, such as the re-definition of ＇the second＇, i.e. one of the seven base units of the international system of units （SI）, test of the time variation of fundamental physical constants and rel- ativity geodesy. Recently, the neutral atom lattice clock has achieved a lower frequency uncertainty com- pared with the optical ion clock, mainly due to the im- provement of the clock laser frequency stability refer- enced to a long high-finesse ULE cavity and the more accurate evaluation of black-body radiation shift. Strontium is an excellent candidate for the neutral atom optical clock. For the fermionic isotope of stron- tium, it has intrinsically less collision shift and the first order Zeeman shift can be removed by an inter- leaved probing approach.Recently, through the pre-cise measurement of the polarizability of strontium, the black body radiation （BBR） shift of the stron- tium lattice clock, which remains to be the limitation factor of its total frequency uncertainty, is reduced to a lower 10^-18 value.The instability of the strontium lattice clock has reached 3.1 × 10-16/√T, showing the significant advantage over the single ion optical clock. The total systematic uncertainty has reached 6.4 × 10^-18 in fractional frequency, which is the best among all optical clocks until now.     

Quartet Pair and Radical Quartet Pair Mechanisms of Electron Spin Polarization Developed within Nonbonded Dimers

Novel mechanisms of the electron spin polarization were reported. Effect of spin-selective interactions within the photo-excited preexisting molecular dimers was utilized. Processes occurring within dimers and upon escape from the dimer cage were considered.     

135La高自旋态的实验研究

利用在束γ谱实验技术,通过¹²⁸Te(¹⁰B,3n)¹³⁵La反应研究了¹³⁵La的高自旋态.基于γγ符合关系、γ射线的相对强度和各向异性度的测量结果,建立了¹³⁵La的能级纲图.在hω≈0.40MeV附近,观测到基于πh_11/2质子轨道上的负宇称带的带交叉.比较N=78同中子素链能级结构的系统性,认为该带交叉是由一对h_11/2准质子发生转动顺排造成的.在高自旋态处,观测到具有很强M1跃迁、Signature劈裂很小的ΔI=1负宇称带,根据系统性认为该带是建立在πh_11/2(νh_11/2)²组态上的γ≈–60°的扁椭球形变带.     

Spin Effects in a Collision of Polarized Protons

The one- and two-spin asymmetries in a collision of polarized protons pp (^*,z) + X are studied in the present work within the framework of the quantum chromodynamics and the electroweak interaction. We use the method of helical amplitudes. Analytical expressions for one-spin A _L and two-spin A _LL asymmetries are derived and their dependences on the transverse momentum of the lepton pair are investigated for three values of invariant mass of the lepton pair. The results obtained allow the spin structure of the proton to be investigated.     

自旋极化的同位旋非对称核物质性质

利用Skyrme有效相互作用,采用核子–核子相互作用参数SKM*和SⅢ对自旋极化的同位旋非对称核物质的特性和状态方程进行了研究,讨论了非对称核物质的磁化率随密度的变化关系及其同位旋依赖性.结果表明:在Skyrme Hartree Fock框架内,同位旋非对称核物质会发生从非极化态到极化态的相变,而且发生相变的临界密度随同位旋非对称度增大而降低.另外,还与微观BHF(Brueckner Hartree Fock)的理论预言进行了比较和讨论.     

钠原子团簇物理学

发展了一个与距离相关的紧密结合分子动力学模型来系统研究钠原子团簇Ｎａｎ的结构、热力学和碰撞动力学性质．计算结果能够很好地符合从头计算法（ａｂｉｎｉｔｉｏｎ）的计算结果和实验结果．同时也探讨了这种有限数目团簇随温度升高可能发生的从类固相到类液相的相变和在碰撞过程中形成双团簇（Ｎａｎ）２的动力学稳定性． Based on the tight binding molecular dynamics, the structural, thermodynamical and collision properties are systematically studied for Nan. Present claculations are successful in reproducing some of the experimental data and in agreement very well with some other ab initio calculations. We also investigate the transition from solid like phase to liquid like phase with increasing temperature for this finite system and the stability of dimer (Nan)2 formed in cluster collisions.     

Experimental Observation of High Spin States in 146Sm Nucleus

High spin states of ¹⁴⁶Sm have been experimentally studied by using ¹³C(95MeV) beam bombarding natural Ba target.Seventeen new γ-rays and eleven new levels were found and assigned to the level scheme of ¹⁴⁶Sm which extends up to 10.2MeV excitation energy.Level structure still shows the characteristics of particle configurations.No long-lived high spin isomer was found up to such high excitation region.     

Hermite Polynomial Representation of the Spin States

We construct the invertible map of the spin-state density operator onto the quasiprobability distribution of three continuous variables. We discuss the connection of this map with two-mode electromagnetic-field oscillators. We give the inversion formula for the spin-density matrix in terms of the Hermite polynomials. We examine the connection of the map constructed with the spin-tomographic representation. We consider the problem of the magnetic-moment rotation in the magnetic field in the suggested representation of spin states.     

Collisions with Participation of Polarized Cesium and Lithium Alkali Atoms

Optics and Spectroscopy - The spin-exchange cross sections and the magnetic resonance frequency shift in collision of lithium and cesium atoms in the ground state are calculated. The calculations...     

自旋极化的对称核物质和中子物质的性质

利用Skyrme有效相互作用对自旋极化的同位旋对称核物质和中子物质的特性进行了研究.用4种核子-核子相互作用参数SⅢ,SKM,SLy230a和SLy230b,分别描绘了核物质状态方程曲线.可以发现不论使用哪一种参数,在自旋极化的同位旋对称核物质和中子物质中都存在着磁化相变转换点.另外还对磁化系数进行了计算,给出了磁化系数比率随密度的变化关系,由于无限不连续点的存在,进一步肯定了在Skyrme-Hartree-Fock理论框架内两种物质会出现磁化相变转换点.     

Spin Squeezing for Superpositions of Dicke States

We investigate spin squeezing for superpositions of Dicke states. We derive the mean spin direction, the length of mean spin, the optimally squeezed angle and numerically calculate the spin squeezing parameter, which is determined by on the superposed coefficients and the relative phase. Approximate same superposed amplitude and the smaller relative phase lead to the larger the length of mean spin, the stronger spin squeezing and spin squeezing maintains in a longer time interval.     

New Construction of Bell States Using Entangled Modified Spin Coherent States

We propose a new construction of Bell states using modified spin coherent states and present the modified spin coherent state of the SU(2) group, along with the discussion of the states proposed.     

Orientation Information from the Dipolar Interaction Between a Complex in the Excited Quartet State and a Doublet Spin Label

An algorithm is proposed for deriving the position of a stable radical relative to a photoexcited quartet state from the electron spin–spin interactions measured by double resonance methods. Intersystem crossing generates multiplet polarization in the quartet state and microwave excitation of the ±3/2 ? ±1/2 transitions converts the multiplet polarization into net polarization of the ±1/2 levels. The dependence of the electron spin echo envelope modulation (ESEEM) of the +1/2 ? ?1/2 transition on the field/frequency of the stimulation pulse is demonstrated. The algorithm is tested by comparing the predicted ESEEM patterns to those from explicit numerical calculations of the spin evolution (so-called numerical experiments), which act as a model for experiment results. The comparison demonstrates that within the point-dipole approximation it is feasible to obtain not only the distance between the two paramagnetic centers but also the orientation of the distance vector relative to the principal axes of the quartet state.     

Energy-Momentum Pseudo-Tensor of Relic Gravitational Wave of Both the Polarized States

Unlike usual celestial gravitational waves, the relic gravitational waves （RGWs） form random signals in curved spacetime background. We calculate the energy-momentum pseudo-tensor of a certain component of the RGWs propagating along arbitrary directions in Cartesian coordinates. It is found that the energy density of RGWs is positive definitely, and the momentum density components have reasonable behaviour. Such results may provide a theoretical basis for the detection of RGWs.     

Spin Polarization of an Ensemble of Alkali Atoms with Zero Average Magnetization

The Landé factors of hyperfine sublevels belonging to the same spectral term differ from each other. This leads to the appearance of an effective gyromagnetic ratio for an atomic ensemble, which can be defined as the ratio of the average magnetic moment to the average angular momentum. Characteristically, this quantity is not a constant, but rather depends on the populations of the hyperfine sublevels. States of an ensemble of atoms occupying their ground level in which the effective gyromagnetic ratio is zero are of much interest. Here, one of such states is considered by the example of alkali metal ⁸⁷Rb. The main idea is to suggest a method for preparing states with zero effective gyromagnetic ratio by means of two-frequency pumping of a saturated alkali-metal vapor in a cell containing a buffer gas. It is noteworthy that, according to calculations, correlation between the two fields is not required for attaining this goal.     

Observation of Electron Spin Resonance in the Microwave-Induced Photovoltage

JETP Letters - The microwave-induced photovoltage in two-dimensional electron systems in an AlAs quantum well and a ZnO/MgZnO heterojunction under the conditions of the quantum Hall effect is...     

The Semiclassical Study of Nuclear High Spin States

Nuclear high spin states are studied in the extended Thomas-Fermi approximation.Explicit formula for rotational energy and various corrections are given.Concrete calculations are performed for three typical nuclei:¹¹⁶Sn,¹⁵⁸Yb and ²⁴⁰Pu.Qualitatively,the results are similar to that of liquid drop model.Quantum corrections to rotational energy (besides shell corrections) cannot be neglected in a quantitative study.     

Correlations of Spin States for Icosahedral Double Group

The irreducible bases of the icosahedral double groups I and I_h are explicitly presented in their respective group spaces. Applying these bases to the spin states |j, , we obtain a simple formula for combining the spin states into the symmetry-adapted bases which belong to a given row of given irreducible representations of I and I_h.     

Generation of Multi-qubit Graph States via Spin Networks

We propose an efficient scheme for preparing multi-qubit graph states via spin networks. The classical types of graph states including cluster state, Greenberger-Horne-Zeilinger state and circle-shaped states can be generated by using imaginary SWAP gate. Our method makes the generation of multipartite entangled graph states more efficient than the ones based on conventional controlled-NOT and controlled phase flip gate for solid-state devices.     

Perfect Transfer of Entangled States on Spin Chain

Current researches have shown that perfect states transfer over arbitrary distances is possible for a simple unmodulated spin chain by some schemes. The transfer of a single qubit state has been investigated in detail by Christandl et al. [Phys. Rev. Lett. 92, 187902(2004)] through a modified Heisenberg XX model Hamiltonian H _G . The previous study of Christandl is restricted to the first-excitation states of H _G (i.e., which correspond to the second subspace of the Hilbert space of H _G ). In this work, we extend their study to the case of the high-excitation states, and find that the entangled states in such a form, | ψ 〉 = α | 00⋯ 0〉 + β | 11⋯ 1〉, can be perfectly transfered on the spin chain. PACS numbers 03.67.Hk, 03.67.Pp, 05.50.+q.