Subjects: Physics >> Nuclear Physics Subjects: Physics >> Atomic and Molecular Physics submitted time 2024-02-22
Abstract： The state-selective single-electron capture process in the collision of N+ ions with He at an energy of 0.64 keV/u has been experimentally studied by the reaction microscopy with a two-fold coincident method, and the state-selective cross-sections and angular distributions of an electron captured into different quantum states of the projectile ions have been obtained. The experimental results show that: the ground state projectile N+(3P) captures a 1𝑠 electron from the He target mainly to the 2𝑝 shell, and the contribution to the higher shells can also be observed; the metastable N+(5S) captures a 1𝑠 electron from the He target mainly to the 2𝑠 shell, with almost no contribution to higher shells. The experimental results are interpreted qualitatively using the potential energy curves of the NHe+ quasimolecular ion, but the reaction window predictions of the molecular Coulomb over-barrier model differ significantly from the experiments. During the capture of the target electron into the 2𝑠 orbital by the metastable projectile N+(5S), a clear oscillatory structure appears in the angular differential cross-section, which is likely to result from Demkov-type transitions.
Subjects: Physics >> Atomic and Molecular Physics submitted time 2023-12-03
Abstract： Experimental and theoretical research on X-ray emissions following charge exchange between slow highly charged ions and atomic Hydrogen supply vital atomic data in the study of diagnosing and simulating plasmas in non-equilibrium astrophysical environment. In the present paper, employing the semiclassical multi-channel Landau-Zener (MCLZ) method, we calculated the total cross-section of bare and hydrogenic C, N, O ions charge exchange with hydrogen atoms, and compared it with previously reported experimental results. In C5 + H collision, theoretically calculated cross-sections have large differences with experimental cross-sections. We also compared state-selective cross-sections calculated by classical MCLZ and quantum-mechanical molecular orbital close-coupling(QMOCC) methods in the solar wind ion velocity (or energy) range. For capture to n = 3 shell, MCLZ calculated state-selective cross-section increase with collision energy increasing; For capture to n = 4 shell, MCLZ calculated state-selective cross-section decrease with collision energy increasing; It is lower than two magnitudes as QMOCC method calculated cross-section. Finally, using the Kronos program package developed in the astrophysical field, we calculated the X-ray emission spectrum, line ratio, and hardness ratio of charge exchange of 1000 eV/u O8 by means of recommended cross-section by Janev, and contrast with the MCLZ method calculated results. We consider that the MCLZ calculation has a large uncertainty, which could affect the accuracy of the astrophysical environment simulation. It is required for developing a more accurate full quantum theory.
Subjects: Physics >> Nuclear Physics Subjects: Physics >> Atomic and Molecular Physics submitted time 2023-06-21
Abstract： The extractions of nuclear charge radii from muonic atom spectroscopy for $^{40}$Ca and $^{208}$Pb are revisited to analyze the model dependencies induced by employing a Fermi-type charge distribution. For that, the charge densities, together with the corresponding muonic transition energies, calculated by the covariant density functional theory are used as a benchmark. The root-mean-square deviation of transition energies is calculated to quantitatively investigate the sensitivities of transition energies to the details of the two-parameter Fermi distribution. It is found that the second and fourth moments of the charge distribution can be extracted accurately from the muonic atom spectroscopy without many model dependencies, whereas the obtained two-parameter Fermi distributions cannot reproduce the details of the benchmarking charge densities and, in particular, its surface-diffuseness parameter cannot be determined accurately with the present experimental uncertainties on the muonic transition energies.
Peer Review Status:
Awaiting Review
Subjects: Physics >> Atomic and Molecular Physics submitted time 2023-04-17
Abstract： The dipole-dipole interaction between atoms and collective effect of atomic ensembles are two hot topics in the research of cold atom physics. While one atom close to another very near, the coherent radiance between atoms will dramatically modify the ensembles’ optical response. This can include, for example, energy levels shift, enhanced or suppressed decay rate and highly dimensional scattering. Since the atoms in ensembles behave as collective rather than independently, we refer this behavior as the collective effect. For the cesium in lower excited states, the atomic distance should be as short as possible in order to achieve strong coupling of atoms via dipole-dipole interaction. In this thesis, we are interested in how to design an experimental system to load the 1D atomic chain in which the atomic distance can be shorter than a half wavelength and investigate how the collective effect changes over the atomic distance.
We design and evaluated a 1D blue-detuned optical dipole traps system, which is consisted of a two-beam interference part and a donut beam part. Then we build the system, capture the 1D atomic chain and investigate the dipole-dipole interaction between two atoms and collective emission of 1D atomic systems. Finally, we simulate how the temperature of atoms influences the collective emission of 1D atomic system in Monte-Carlo method theoretically.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrometry Subjects: Library Science，Information Science >> Information Science Subjects: Physics >> Atomic and Molecular Physics submitted time 2021-03-05
Abstract： " Gravitational wave signals were directly detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015, bring hope to new physics and astrophysics and setting off a new wave of the development of laser interferometer gravitational wave detectors. In the background of the vigorous development of the interferometer gravitational wave detectors from ground to space, a comparative study of each detector are carried out from the aspects of construction history, technical characteristics and development positioning, and operation mode. And the experiences and enlightenments of the construction and operation of laser interferometer gravitational wave detectors are further summarized, namely: the construction of laser interferometer gravitational wave detector is a long-term project, which helps to promote the perfect development of scientific research fault tolerance mechanism and scientific evaluation mechanism; the construction of gravitational wave detector is a high-tech project, which helps to promote the coordinated development of multidisciplinary technologies; the construction of laser interferometer gravitational wave detectors is an international project, which helps to promote the healthy development of scientific research cooperation.
Peer Review Status:Awaiting Review
Subjects: Physics >> Atomic and Molecular Physics Subjects: Chemistry >> Chemical Physics submitted time 2018-05-19
Abstract：
See the paper
Peer Review Status:Awaiting Review
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Physics >> Atomic and Molecular Physics submitted time 2016-12-10
Abstract：通常的狭义相对论是在庞加莱变换下不变的，它的基本度规为闵科夫斯基时空度规，该度规满足没有宇宙学常数Λ的真空爱因斯坦方程。本文指出：Λ≠0 时的狭义相对论是德西特/反德西特不变狭义相对论。求解Λ≠0的真空爱因斯坦方程，得到这种拓展的狭义相对论的基本度规是陆启铿-邹振隆-郭汉英1974年提出的Beltrami 度规；用欧拉-拉格朗日方程证明Beltrami时空的自由粒子运动是惯性运动。本文求出了德西特/反德西特不变狭义相对论的全部凯林(Killing) 矢量，证明了Beltrami 时空是最大对称性空间。导出来全部守恒量。构造了理论的正则形式，发现了正、负正则能量的色散关系的不对称性；实现了正则量子化，导出了相对论性波方程，从而建立了德西特/反德西特不变的相对论量子力学。简要介绍了通过天文观测原子（或离子）能级劈裂来探测精细结构常数#11;改变的实验。实验结果在4 ∼ 5σ 置信度内否定了庞加莱不变狭义相对论的预言，发现在z ≈ {1 ∼ 3}处αz ̸= α0。由于原子或离子能级的精细结构是相对论量子力学的结果，所以观测实验支持在红移z ≥ 1的狭义相对论量子力学中的Λ修正不可忽略。这是对德西特/反德西特不变狭义相对论的实验支持。是超出现有物理学标准模型的新物理。
Peer Review Status:Awaiting Review
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