Superexchange-mediated magnetization dynamics with ultracold alkaline-earth atoms in an optical lattice

Superexchange and inter-orbital spin-exchange interactions are key ingredients for understanding(orbital) quantum magnetism in strongly correlated systems and have been realized in ultracold atomic gases.Here we study the spin dynamics of ultracold alkaline-earth atoms in an optical lattice when the two exchange interactions coexist.In the superexchange interaction dominating regime,we find that the time-resolved spin imbalance shows a remarkable modulated oscillation,which can be attributed to the interplay between local and nonlocal quantum mechanical exchange mechanisms.Moreover,the filling of the long-lived excited atoms affects the collapse and revival of the magnetization dynamics.These observations can be realized in state-dependent optical lattices combined with the state-of-the-art advances in optical lattice clock spectroscopy.     

Parameter analysis for a nuclear magnetic resonance gyroscope based on bf133Cs-129Xe/131Xe

We theoretically investigate several parameters for the nuclear magnetic resonance gyroscope based on ¹³³Cs-¹²⁹Xe/¹³¹Xe. For a cell containing a mixture of ¹³³Cs at saturated pressure, we investigate the optimal quenching gas (N₂) pressure and the corresponding pump laser intensity to achieve 30% ¹³³Cs polarization at the center of the cell when the static magnetic field B₀ is 5 μT with different ¹²⁹Xe/¹³¹Xe pressure. The effective field produced by spin-exchange polarized ¹²⁹Xe or ¹³¹Xe sensed by ¹³³Cs can also be discussed in different ¹²⁹Xe/¹³¹Xe pressure conditions. Furthermore, the relationship between the detected signal and the probe laser frequency is researched. We obtain the optimum probe laser detuning from the D2 (6²S_1/2→6²P_3/2) resonance with different ¹²⁹Xe/¹³¹Xe pressure owing to the pressure broadening.     

Positronium Spin-Conversion Reactions Promoted by 3d Complexes in Highand Low-Spin States

Continuing in our work on the correlations between the rate constants, k _CR, of the ortho into para-positronium conversion reactions, CR, promoted by complexes of various 3d ions and the metal electron delocalization caused by the ligands, the relationship between the parameters of the correlation lines pertinent to highand low-spin complexes of Cr^II, Mn^II, and Co^II ions was ascertained. Moreover, it was experimentally verified, for the first time, that the statistical probability of the CR promoted by paramagnetic compounds with S = 1/2 is three times larger than that of the CR caused by compounds with S > 1/2.     

Scattering amplitude and two-body loss of ultracold alkaline-earth atoms in a shaking synthetic magnetic field

The idea of manipulating the interaction between ultracold fermionic alkaline-earth (like) atoms via a laser-induced periodical synthetic magnetic field was proposed in Kanász-Nagy et al (2018 Phys. Rev. B 97, 155156). In that work, it was shown that in the presence of the shaking synthetic magnetic field, two atoms in ¹S₀ and ³P₀ states experience a periodical interaction in a rotated frame, and the effective inter-atomic interaction was approximated as the time-averaged operator of this time-dependent interaction. This technique is supposed to be efficient for ¹⁷³Yb atoms which have a large natural scattering length. Here we examine this time-averaging approximation and derive the rate of the two-body loss induced by the shaking of the synthetic magnetic field, by calculating the zero-energy inter-atomic scattering amplitude corresponding to the explicit periodical interaction. We find that for the typical cases with shaking angular frequency λ of the synthetic magnetic field being of the order of (2π) kHz, the time-averaging approximation is applicable only when the shaking amplitude is small enough. Moreover, the two-body loss rate increases with the shaking amplitude, and is of the order of 10⁻¹⁰ cm³ · s⁻¹ or even larger when the time-averaging approximation is not applicable. Our results are helpful for the quantum simulations with ultracold gases of fermionic alkaline-earth (like) atoms.     

Magnetic and Electrochemical Properties of a TEMPO‐Substituted Disulfide Diradical in Solution,in the Crystal,and on a Surface

A study of the magnetic and electrochemical properties of a TEMPO‐substituted disulfide diradical in three different environments was carried out: in solution, in the crystal, and as a self‐assembled monolayer (SAM) on an Au(111) substrate, and the relationship between them was explored. In solution, this flexible diradical shows a strong spin‐exchange interaction between the two nitroxide functions that depends on the temperature and solvent. Structural, dynamic, and thermodynamic information has been extracted from the EPR spectra of this dinitroxide. The magnetic interactions in the crystal include intra‐ and intermolecular contributions, which have been studied separately and shown to be antiferromagnetic in both cases. Finally, we demonstrate that both the magnetic and electrochemical properties are preserved upon chemisorption of the diradical on a gold surface. The resulting SAM displayed anisotropic magnetic properties, and angle‐resolved EPR spectra of the monocrystal allowed a rough determination of the orientation of the molecules in the SAM.     

超极化气体肺部磁共振成像

磁共振成像(MRI)技术具有非侵入、无放射性的特点,在临床疾病诊断中具有独特的优势,但是肺部空腔的特殊结构使传统质子MRI无法对其直接成像.自旋交换光抽运(SEOP)方法可以使惰性气体原子的极化度增强4个量级以上,从而使肺部的气体MRI成为可能.该文介绍了超极化惰性气体肺部MRI的最新研究进展,包括超极化气体磁共振相关参数的测量方法、肺部通气结构成像、肺部气体交换功能成像,同时比较了常用于肺部MRI气体的优点和缺点.     

Spin dynamics of the potassium magnetometer in spin-exchange relaxation free regime

The laser-pumped potassium spin-exchange relaxation free(SERF) magnetometer is the most sensitive detector of magnetic field and has many important applications. We present the experimental results of our potassium SERF magnetometer. A pump–probe approach is used to identify the unique spin dynamics of the atomic ensemble in the SERF regime.A single channel sensitivity of 8 f·THz-1/2is achieved with our SERF magnetometer.     

吡唑-3,5-二(N-烷基甲酰胺)类配体的双核铜配合物的合成和结构

合成了吡唑-3,5-二(N-烷基甲酰胺)(LH_3)的一系列配合物:(LH_2)_2Cu_2(NO_3)_2·H_2O,L_2Cu_2Na_2·nH_2O。得到了(PEAH_2)_2Cu_2(NO_3)_2·H_2O的单晶结构。(PEAH_3代表吡唑-3,5-二(N-乙基甲酰胺))。从元素分析及红外光谱讨论了不同pH时配合物的配位形式。配合物的ESR谱表明了分子内两个Cu原子间有自旋交换作用。     

On the positronium spin conversion reactions caused by some macrocyclic Co complexes

The rate constants, k_CR, of ortho- into para-positronium (o-Ps→p-Ps) spin conversion reactions, CR, caused by the high-spin [Co^IIsep]²⁺, [Co^IIdinosar]²⁺ and [Co^IIdiamsar]²⁺ macrocyclic complexes and also by high-spin [Co^II sen]²⁺ tripod complex were measured at several temperatures. The delocalizations, β, of Co^II unpaired electrons, promoted by the mentioned ligands, were determined by using the previously established correlations between k_CR and the electron delocalization β of unpaired metal electrons. β is given by the ratio between the Racah inter-electronic repulsion parameters of complexes, B, and that of the free ions, B₀. The β values are compared with those of the Co^II complexes with en (1,2-ethanediamine), pn (1,2 propanediamine) and dien (2,2′ diamino diethylamine) ligands. The k_CR rate constants are also compared with those of the Ps oxidation reactions, OR, promoted by the corresponding Co^III complexes. It is concluded that, unlike OR's, the CR's do not occur by formation of hepta-coordinate adducts with Ps atoms.     

吡唑-3,5-二(N-烷基甲酰胺)类配体的双核铜配合物的合成和结构

合成了吡唑-3,5-二(N-烷基甲酰胺)(LH₃)的一系列配合物:(LH₂)₂Cu₂(NO₃)₂·H₂O,L₂Cu₂Na₂·nH₂O。得到了(PEAH₂)₂Cu₂(NO₃)相似文献