Electromagnetically Induced Transparency in a Cold Gas with Strong Atomic Interactions

Electromagnetically induced transparency （EIT） is investigated in a system of cold, interacting cesium Rydberg atoms. The utilized cesium levels 6S1/2, 6P3/2 and nD5/2 constitute a cascade three-level system, in which a coupling laser drives the Rydberg transition, and a probe laser detects the EIT signal on the 6S1/2 to 6/23/2 transition. Rydberg EIT spectra are found to depend on the strong interaction between the Rydberg atoms. Diminished EIT transparency is obtained when the Rabi frequency of the probe laser is increased, whereas the corresponding linewidth remains unchanged. To model the system with a three-level Linclblad equation, we introduce a Rydberg-level dephasing rate γ3 = κ×（P33/Ωp）^2, with a value κ that depends on the ground-state atom density and the Rydberg level, The simulation results are largely consistent with the measurements. The experiments, in which the principal quantum number is varied between 30 and 43, demonstrate that the EIT reduction observed at large Ωp is due to the strong interactions between the Rydberg atoms.

Experimental study of cross-section ratios in the collisions of C^(q+) and O^(q+) (q=1-4) on atomic helium in strong-interaction region

We have measured the cross-section ratios of helium induced by Cq＋ and Oq＋ （q = 1-4） in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method combined with the MPA-3 data acquisition system. Hence, we obtain the ratios of total single-ionization cross-sections （SI, SC, SLSI, and DLSI）, total double-ionization cross-sections （DI, DC, TI, SLDI, and DLDI） and cross-sections of every process （SI, SC, SLSI, DLSI, DI, DC, TI, SLDI, and DLDI）, which induce the single-ionization and double-ionization, to the total cross sections respectively. The competitive relations between the reaction-channels and the experimental data law of each reaction-channel are revealed explicitly, and the qualitative explanations involved in those results are also presented accordingly.

Calculation of the Duration of the Atomic Tunneling Ionization in a Strong Electrostatic Field by Using Bohmian Trajectories Approach

The duration of a bound electron tunneling through the barrier formed by atomic potential and electrostatic field is calculated by the Bohmian trajectories scheme. The time of the tunneling ionization decreases with the increase of the amplitude of the electrostatic field. By using the information about the position, velocity and force of the Bohmian trajectories, the dynamical process of tunneling through the barrier is investigated.

A Generic Description Model for the Structure of Atomic Nucleus with New Interpretation of the Strong Forces

The present investigation is motivated by finding and developing an easily understandable solution in the context of unified quantum and gravitational theories. Model-based methods are applied, with emphasis on structural descriptions by introducing some strong hypotheses. A subset of the introduced hypotheses led to a surprising understanding of the internal structure and construction of quarks, neutrons, protons and more complex atomic nuclei. The research work therefore focused mainly on the model-based interpretation of subatomic processes. The results obtained so far and presented in this paper are new. They consist of a generic description model for the structure of atomic nuclei. This model contains two important structural links that originate from the initial phase of the cosmological big bang. They hold atomic parts together and are involved in many known nuclear fusion and fission processes. Modifications of them, including the electron-positron annihilation process, are necessary and will be described. A new interpretation of the strong forces from the Standard Model is possible and will be given. In addition, the formation processes for electron and positron particles are considered. Based on the structural relationships, a deeper understanding of matter transformations (transmutations), early cosmological processes and dark matter has been achieved. All challenges of this work are the logical conclusions from the used hypotheses on two structural links. They need to be further investigated and verified by theoretical and experimental works. The postulated particle in this paper, as accompanying product in the electron-positron annihilation, will play a major role for the future investigations.

Two-Parameter Banach Space Valued Strong Martingales and Characterizations of p-Smoothable Spaces

In this paper we introduce the concept of two-parameterB-valued strong martingales and investigate some features of these strong martingales. We also characterizep-smoothable Banach spaces in terms of these strong martingales.

Strong-Driving-Assisted Probabilistic State Preparation in Cavity QED

An alternative scheme is proposed for preparing the superpositions of coherent states with controllable weighting factors along a straight line for a cavity field. The scheme is based on the interaction of a single-mode cavity field with a resonant two-level atom driven by a strong classical field. It is in contrast to the previous methods used in cavity QED of injecting a coherent state into a cavity via a microwave source. In the scheme, the interaction between the cavity mode and atoms is fully resonant, thus the required interaction time is greatly shortened. Moreover, the present scheme requires smaller numbers of operations. In view of decoherence, a reduction of interaction time and numbers of operations for the state preparation is very important for experimental implementation of quantum state engineering.

Accurate calculations of the helium atom in magnetic fields

The 1^10^＋ 1^1（-1）^＋and 1^1（2）^＋ states of the helium atom in the magnetic field regime between 0 and 100 a.u. are studied using a full configuration-interaction （CI） approach. The total energies, derivatives of the total energy with respect to the magnetic field and ionisation energies are calculated with Hylleraas-like functions in spherical coordinates in low to intermediate fields and Hylleraas Caussian functions in cylindrical coordinates in intermediate to high fields, respectively. In intermediate fields, the total energies and ionisation energies are determined in terms of Hermite interpolation, based on the results obtained with the two above-mentioned basis functions. Calculations show that the current method can produce lower total energies and larger ionisation energies, and make the two ionisation energy curves obtained with the two above-mentioned basis functions join smoothly in intermediate fields. Comparisons are also made with previous works.

A Novel Elementary Particle Theory Based on External Energy Absorbed and Re-Emitted by Atoms

In this study, all energy in the universe, here called energy quanta, originates from a singularity at the centre of the universe. The electron and the atom are completely passive;they absorb energy quanta by means of forced damped oscillators and the absorbed energy quanta are then re-emitted. Absorbed and stored energy quanta result in nuclear energy. Re-emitted energy quanta are fields. Re-emitted energy quanta operating on oscillators, in adjacent particles and atoms, result in forces: strong force, Coulomb force and gravitational force. Using this model may enable unification of elementary particle physics, general relativity, electromagnetic theory and quantum physics into one comprehensive theory.

Atoms Absorb Low Frequency Electromagnetic Energy

This paper presents a method to measure TEM (transverse electromagnetic) waves absorbed by atoms. The results show the existence of a singularity in the universe which generates a broad spectrum of synchronized and extremely low frequency TEM waves in the period range 30 - 160 s. Atoms create resonance and absorb these TEM waves. The absorbed energy consists of a set of TEM waves where the sum generates an intrinsic static electric and magnet field. It is proposed that this static electric and magnetic field induces static forces within the atomic nucleus. The study describes a method to measure TEM waves absorbed by atoms (direction, frequency and amplitude). The study displays that chemical elements absorb TEM waves of different periods, supporting the hypothesis that TEM waves are absorbed by an atomic intrinsic resonance mechanism. The study displays a non-invasive method facilitating novel analyses of the atomic nucleus.

A Novel Model of the Atom

In this study all energy in the universe, here called energy quanta, originate from a singularity at the centre of the universe. These energy quanta have different frequencies and at each frequency the energy quanta can have positive or negative spin direction. There is a force of attraction between energy quanta which have exactly the same frequency but opposite spins. This is the dominating force in the universe and accounts for the strong nuclear force, the Coulomb force and the gravitational force. The universe contains one more basic entity;the oscillator quantum which absorbs and re-emits energy quanta at one specific frequency. The oscillator quantum can have positive or negative spin. Thus, there is a force of attraction between oscillator quanta with opposite spins and which amalgamates oscillator quanta into larger structures, i.e. particles (e.g. electron). These particles also have spin at a specific spin frequency and they have positive or negative spin. Thus they absorb and re-emit energy quanta at a frequency specific to the particle and where they can have positive or negative spin. This amalgamates particles into larger structures, e.g. quarks, neutron, proton and atomic nucleus. Using this model enables simple and stringent descriptions of elementary particle physics, electromagnetic theory, gravity, photon and inertial mass. The present model may be a step towards unification of elementary particle physics, general relativity, quantum physics and electromagnetic theory into one comprehensive theory.

Molecular Structure of Atomic Nucleus

In this work, we extend our work on the Heisenberg model of the neutron formulated as a dwarf hydrogen-like atom under the influence of the More General Exponential Screened Coulomb Potential (MGESCP) to show that an atomic nucleus may possess a molecular structure made up of atoms bonding together by a potential used to describe the strong force associated with a generalised Yukawa MGESCP potential. We show that the neutrons and protons are arranged into narrow lattices therefore they may fold to form three-dimensional shells by bonding similar to hydrogen bonding. In particular, the nucleons may form stable structures such as that of fullerenes in which the vertices are occupied by the nucleons which are simply just protons. For example, a nucleus with a total number of 60 nucleons may arrange itself into the topological structure of a buckminsterfullerene. We also apply Schrödinger wave equation with central field approximation to describe the quantum dynamics of nuclei of atomic atoms that now possess the physical structure of a dwarf molecular ion.

Demonstration of the approximation of eliminating atomic excited populations in an atom-cavity system

Using the master equation approach to a V-type three-level atom inside a high-finesse single-mode cavity in the strong coupling condition, we demonstrate the approximation of eliminating populations of atomic excited states, which is widely used in the field of the atom cavity systems [Hechenblaikner G, Gangl M, Horak P and Ritsch H 1998 Phys. Rev. A 58 3030]; Liu L W, Tan T and Xu Y 2008 J. Mod. Opt. 56 968; Cho J, Angelakis D G and Bose S 2008 Phys. Rev. A 78 062338. This is reflected in the deviation of the population 5, of which the value is 10^-3 - 10^-2. We further find the deviation of the dipole force and demonstrate that the deviation of atomic population will not notably affect the dipole force of the atom in the strong coupling condition. A relevant experimental case is also presented.

硫酸化氧化锆负载的Ru单原子催化甲烷直接转化制甲醇

天然气作为一种低碳清洁能源,其储量大、价格低、热值高,被认为是最有前途的石油替代资源之一.甲烷是天然气的主要成分,直接转化为甲醇是有效利用甲烷的一种途径,也是一个极具挑战性的课题.一方面,甲烷的C-H键(439.3 kJ^·mol^(-1))强度非常高,活化十分困难;另一方面,在反应条件下,甲醇等产物比甲烷更容易被氧化,从而导致目标产物的选择性不高.因此,设计高效催化剂是解决该难题的有效途径之一.研究(J. Catal., 1993, 144.238-253和Catal. Today, 2021, 365,71-79)发现,硫酸化的氧化锆(SZ)负载的贵金属(例如Pt等)等超强酸催化剂能够促进甲烷在脱氢芳构化反应中的活化.受该工作启发,本文通过模拟均相催化设计了固体超强酸负载的Ru单原子催化剂(SAC),并在温和条件(70 ℃)下将其用于甲烷直接转化制甲醇反应.结果发现,在Ru/SZSAC上的含氧化合物(CH_(3)OH, CH_(3)OOH和HCOOH)收率(18.32 μmol,≥80 h^(-1))显著超过SZ(0.67 μmol)和Ru/ZrO_(2)(0.29 μmol),这表明在Ru/SZSAC上形成了新的活性中心.结合^(13)CH_(4)同位素标记实验、吡啶吸附红外光谱(PY-IR)、电子顺磁共振(EPR)和X射线光电子能谱(XPS)等表征结果,提出了Ru单原子和超强酸位点协同催化甲烷转化制甲醇的反应机理.首先,通过AC-HADDF-STEM证明了Ru/SZSAC的成功制备;PY-IR谱和氨气程序升温脱附结果证明了在该体系中硫酸化处理有效增加了催化剂表面的强酸位点(包括B-酸和L-酸).EPR结果表明,与ZrO_(2)和0.1Ru/ZrO_(2)相比,在SZ和0.1Ru/SZ上产生更多^(·)OH.进一步结合催化剂表面酸性变化情况和文献报道说明,催化剂表面的强酸位点(包括B-酸和L-酸)可以促进H_(2)O_(2)有效分解成^(·)OH和^(·)OOH,而^(·)OH在甲烷活化的过程中起着至关重要的作用,这合理解释了0.1Ru/SZ比0.1Ru/ZrO_(2)催化性能更好的原因.结合XPS结果推测,硫酸根的强吸电子作用使与其相邻的Ru^(δ+)和Zr^(γ+)的价态都高于+4 (δ> 4, γ> 4).综上提出了Ru^(δ+)和Zr^(γ+)协同催化甲烷C-H键断裂的反应机理:CH_(4)和H_(2)O_(2)分别在Ru^(δ+)和Zr^(γ+)上形成Ru^(δ+)-CH_(4)和Zr^(γ+)-^(·)OH;然后, Zr^(γ+)-^(·)OH提取相邻Ru^(δ+)-CH_(4)的氢原子并生成CH_(3)OH.Ru单原子与SZ的协同作用有效地促进了CH_(4)向C1含氧化合物的转化,这为设计高效的多功能协同催化甲烷直接转化制甲醇反应的SACs开辟了新途径.

微光学腔内单原子的俘获及其耦合强度的精确调控

通过在长度为336μm的光学法布里-珀罗腔内构建单个微尺度光学偶极阱,实现了腔内单个原子的俘获,俘获寿命为(2.60±0.18)s,从而实现了稳定的单原子与光学腔强耦合的腔量子电动力学系统.通过腔的透射光场能够实现光学阱中单原子俘获事件的检测,准确率为98.5%.实验通过精确控制俘获的单原子位置实现了单原子与腔模耦合强度在三维方向的精确调控,测量了不同耦合强度下的单原子真空拉比分裂谱.

强激光场驱动的原子里德堡态激发及电离(特邀)

强场飞秒激光作用于原子时,原子中的电子除了发生多光子电离、隧穿电离等过程外,还有很大的概率处于高激发态。这种高激发态的原子在超强超短激光场中非常稳定,并且与强场中的其它许多现象密切相关,例如,中性粒子加速、多光子拉比振荡、近阈值谐波辐射等,因此近十几年来是强场超快物理领域的研究热点之一。在这些研究中,强激光场中里德堡原子的产生机制、激光对里德堡态的调控、里德堡态强场电离及稳定性等,是关注的主要问题。本文将概述强激光驱动的里德堡态的产生机制,包括多光子共振激发,受挫隧穿电离等。重点介绍强激光场驱动的里德堡态原子激发过程中的多种干涉现象。这些干涉现象提供了里德堡原子强场激发的动态过程信息。同时,还将介绍激发态原子在强激光场中的电离过程,特别是圆偏光驱动的里德堡原子电离的圆二色性。

强噪声条件下原子重力仪小波降噪适应性研究

为消除海洋原子重力仪测量数据中的强背景噪声,提升海洋重力场测定精度,研究了不同阈值量化方法下小波降噪算法在海洋原子重力仪数据处理中的适用性问题。首先,通过仿真试验,以数字滤波器作参考,比较了多种阈值计算方法、多种阈值选取规则下的小波降噪算法对不同强背景噪声的滤波效果,指明了最适合用于船载原子重力仪测量数据降噪的阈值量化方法;然后,结合本课题组的湖上动态测量数据,对仿真试验得到的结论加以验证。结果表明:强背景噪声条件下,小波降噪的滤波效果受阈值量化方法选择的影响会有很大的差异,不同阈值计算方法中,固定阈值计算方法对应的降噪效果最好,滤波后信号信噪比至少提升49 dB,精度较数字滤波器至少提升7.6%;不同阈值选取规则中,软阈值选取规则对应的降噪效果最好,无需利用改进阈值选取规则进行优化。

单原子催化剂中金属-载体强相互作用综述

单原子催化由于其独特的特性近年来在多相催化领域引发很大的关注。均匀分散的单原子可以作为催化活性中心,为实现催化反应的高选择性、高活性和研究其催化反应机理提供很大的可能。随着催化剂尺寸的逐步减小,催化剂的表面原子结构、电子结构和缺陷将发生明显变化,常常会产生金属-载体强相互作用。结合近年来单原子催化领域的研究工作,综述了单原子催化剂中金属-载体强相互作用的研究进展。介绍了单原子催化剂中金属-载体强相互作用的具体类型和表现形式,包括金属-金属相互作用、空隙或缺陷锚定、金属阳离子配位和有机配体络合。最后,基于对单原子催化剂中金属-载体强相互作用的理解和认识,对该研究领域的发展趋势和关键问题进行了展望。

强阴离子交换柱分离-氢化物发生-原子荧光光谱法测定水中As(Ⅲ)和As(Ⅴ)

本文报道水中As（Ⅲ）和As（Ⅴ）的Supelco强阴离子交换（SAX）柱分离-氢化物发生-原子荧光光谱（HG—AFS）法检测的新方法。方法的检出限为0．0466μg／L，相对标准偏差为0．89％～1．01％，加标回收率为95．10％～105．30％。该方法具有操作简单，分离效果好，测定精确度、准确度高等优点。将其应用于水样分析，可测定水中砷的不同价态。

强场与级联型三能级原子相互作用中原子的偶极压缩效应

采用数值计算方法研究了强相干初态光场与级联型三能级原子相互作用中原子的偶极压缩效应 结果表明 :级联型三能级原子偶极算符的两个正交分量均呈现出周期性的压缩现象 ,原子存在偶极压缩 ,且压缩的最大深度比弱场作用情况下要深得多 ;随着 n值的不断增大 ,偶极算符两个正交分量的振荡频率随之增大 ,场与原子的非线性耦合越来越强 。

微波强场中的光谱激发现象

本文报道了元素、化合物和放电灯在微波强场中产生的激发现象。介绍了一种在微波强场中产生原子发射光谱的新方法。采用作者自行改制的微波激发装置，既可使固态的元素和化合物产生光谱辐射，也可使各种放电灯和气体光谱管得以激发，用一种装置实现了几种装置的功能。对于该方法存在的问题，文中也作了一定的说明。