Mono‐ and Dinuclear Heteroleptic Cobalt Complexes with α‐Diimine and Polyarene Ligands

Reactions of the dimeric cobalt complex [(L^?Co)₂] ( 1 , L=[(2,6‐iPr₂C₆H₃)NC(Me)]₂) with polyarenes afforded a series of mononuclear and dinuclear complexes: [LCo(η⁴‐anthracene)] ( 2 ), [LCo(μ‐η⁴:η⁴‐naphthalene)CoL] ( 3 ), and [LCo(μ‐η⁴:η⁴‐phenanthrene)CoL] ( 4 ). The pyrene complexes [{Na₂(Et₂O)₂}{LCo(μ‐η³:η³‐pyrene)CoL}] ( 5 ) and [{Na₂(Et₂O)₃}{LCo(η³‐pyrene)}] ( 6 ) were obtained by treating precursor 1 with pyrene followed by reduction with Na metal. These complexes contain three potential redox active centers: the cobalt metal and both α‐diimine and polyarene ligands. Through a combination of X‐ray crystallography, EPR spectroscopy, magnetic susceptibility measurement, and DFT computations, the electronic configurations of these complexes were studied. It was determined that complexes 2 – 4 have a high‐spin Co^I center coupled with a radical α‐diimine ligand and a neutral polyarene ligand. Whereas, the ligand L in complexes 5 and 6 has been further reduced to the dianion, the cobalt remains in a formal (I) oxidation state, and the pyrene molecule is either neutral or monoanionic.     

Monte Carlo study of the universal area distribution of clusters in the honeycomb O（n） loop model

We investigate the area distribution of clusters (loops) in the honeycomb O(n) loop model by means of the worm algorithm with n = 0.5, 1, 1.5, and 2. At the critical point, the number of clusters, whose enclosed area is greater than A, is proportional to A-1 with a proportionality constant C. We confirm numerically that C is universal, and its value agrees well with the predictions based on the Coulomb gas method.     

Time-domain Ramsey interferometry with Bose–Einstein condensates

We report on the observation of time-domain interference with Bose–Einstein condensates, by means of a double separated oscillator technique. We discuss the decay of the Ramsey oscillations amplitude, that in our system occurs on a time scale of tens of microseconds. To elucidate the origin of this fast decay, we compare the behaviour of a condensate with that of a thermal cloud.     

氮气在100 eV以下的绝对振子强度密度

在入射电子能量为2500 eV、能量分辨为100 meV的条件下，得到了氮气在100 eV以下的绝对光学振子强度密度和广义振子强度密度；得到了23 eV和31.4 eV两个超激发态的绝对广义振子强度、并讨论了它们的动量转移依赖特性。     

基于金刚石氮-空位色心的精密磁测量

磁是一种重要的物理现象,对其进行精密测量推动了许多科技领域的发展.各类测磁技术,包括霍尔传感器、超导量子干涉仪、自旋磁共振等,都致力于提升空间分辨率和灵敏度.近年来,金刚石中的氮-空位色心广受关注.这一固态单自旋体系具有许多优点,例如易于初始化和读出、可操控、具有较长相干时间等,这使得它不仅在量子信息、量子计算等领域崭露头角,而且在量子精密测量上显现出巨大的应用前景.基于氮-空位色心,利用动力学解耦、关联谱等技术,已实现若干高灵敏度、高分辨率的微观磁共振实验,其中包括纳米尺度乃至单分子、单自旋的核磁共振和电子顺磁共振.氮-空位色心也可以用于微波和射频信号的精密测量.本文对围绕上述主题开展的一系列研究工作进行综述.     

Electron Momentum Spectroscopy of Outer Valence Orbitals of 2-Fluoroethanol

The binding energy spectra and electron momentum distributions for the outer valence molecular orbitals of gaseous 2-fluoroethanol have been measured by the non-coplanar asymmetric (e, 2e) spectrometer at impact energy of 2.5 keV plus binding energy. The quantitative calculations of the ionization energies and the relevant molecular orbitals have been carried out by using the outer-valence Green’s function method and the density functional theory with B3LYP hybrid functional. The observed ionization bands in binding energy spectra, as well as the previous photoelectron spectrum which was not assigned, have been assigned for the first time through the comparison between experiment and theory. In general, the theoretical electron momentum distributions calculated by B3LYP method with aug-cc-pVTZbasis set are in line with the experimental ones when taking into account the Boltzmannweighted thermo-statistical abundances of five conformers of 2-fluoroethanol.     

Thermal Quantum Discord in Pure Dzyaloshinskii-Moriya Model with Magnetic Field

We investigate the effects of the directions of Dzyaloshinskii-Moriya (DM) interaction vector and magnetic field on the quantum discord in the pure DM model. For different directions of DM vector, we find that there are different optimal parameter components of magnetic field. Moreover, we find that the optimal parameter components rules are the same for the Hamiltonian H₁ and H₂. According to the rules, for a certain axial DM vector, we can get the maximal quantum discord by adjusting the direction of the external magnetic field, which is feasible under the current experimental technology.     

Geometric measure of quantum discord and the geometry of a class of two-qubit states

We investigate the geometric picture of the level surfaces of quantum entanglement and geometric measure of quantum discord(GMQD) of a class of X-states, respectively. This pictorial approach provides us a direct understanding of the structure of entanglement and GMQD. The dynamic evolution of GMQD under two typical kinds of quantum decoherence channels is also investigated. It is shown that there exists a class of initial states for which the GMQD is not destroyed by decoherence in a finite time interval. Furthermore, we establish a factorization law between the initial and final GMQD, which allows us to infer the evolution of entanglement under the influences of the environment.     

Quantum effects on elastic collisions in a two-component plasma

Eikonal method is applied to investigate the quantum effects on elastic electron–ion collisions in a two-component plasma. An effective Kelbg potential model taking into account the classical effect as well as the quantum-mechanical effect is applied to describe the electron–ion interactions in a two-component plasma. The impact parameter method is applied to represent the path of the projectile electron in order to investigate the variation of the eikonal cross section as a function of the impact parameter, thermal de Broglie wavelength, and projectile energy. In the second-order eikonal approximation, the quantum effects significantly reduce the elastic electron–ion scattering cross section. It is also found that the second-order eikonal phase is caused by the pure quantum mechanical effects.     

Positron-Impact Excitation of Hydrogen Atoms in Debye Plasmas

The positron-impact excitation of hydrogen atoms embedded in plasma environments is investigated using the close-coupling approximation from the low to intermediate energy region without including any positronium formation channel, and the excitation cross sections for 1s→2s, 1s→2p and 2s→2p processes are calculated in a wide Debye parameter range. The screening interactions, described by the Debye-Hückel model, decrease the coupling matrix elements, resulting in the reduction of the excitation cross sections from a few percent to one magnitude of ten. This will alter remarkably the spectroscopy of hydrogen in intensity and position, which should be considered in the simulation and diagnostics under some specific plasma conditions.