Author

# Yuan-Chen Xu

Bio: Yuan-Chen Xu is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Valence electron & Atomic physics. The author has an hindex of 3, co-authored 9 publications receiving 22 citations.

##### Papers

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TL;DR: The generalized oscillator strengths of the valence-shell excitations of HCl have been measured at an incident electron energy of 1500 eV and an energy resolution of 70 meV, and their momentum transfer dependence behaviors have been elucidated.

Abstract: The oscillator strengths and integral cross sections of the valence-shell excitations of HCl have significant applications in the studies of planetary atmospheres and interstellar gases. In the present work, the generalized oscillator strengths of the valence-shell excitations of HCl have been measured at an incident electron energy of 1500 eV and an energy resolution of 70 meV, and their momentum transfer dependence behaviors have been elucidated. It is observed that the generalized oscillator strength ratios of the b3Π1(ν' = 0) state to the C1Π(ν' = 0) state are a constant and independent of the squared momentum transfer, and this typical behavior in the momentum space is explained by the intraconfiguration mixing of the b3Π1 and C1Π states due to the spin-orbital interaction. The optical oscillator strengths of the valence-shell excitations have been obtained by extrapolating the generalized oscillator strengths to the limit of zero squared momentum transfer. The present optical oscillator strengths give an independent cross-check to the previous experimental and theoretical results, and it is found that most of the photoabsorption measurements are limited by the line saturation effect. The integral cross sections of the valence-shell excitations of HCl have been obtained systematically from the threshold to 5000 eV with the aid of the BE-scaling method.

8 citations

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TL;DR: The comprehensive comparison of the present results with the previous experimental and theoretical ones shows that the high-energy limit has been reached at an impact electron energy of 1500 eV in K2 < 1 a.u, and the minimum position of the generalized oscillator strength of the vibronic state shifts toward the larger squared momentum transfer with the increasing vibrational quantum number.

Abstract: The vibrationally resolved generalized oscillator strengths of the first and strongest singlet excitation AA2″1← X1A1 of ammonia have been determined at an impact electron energy of 1500 eV with an energy resolution of 80 meV. The comprehensive comparison of the present results with the previous experimental and theoretical ones shows that the high-energy limit, where the first Born approximation holds, has been reached at an impact electron energy of 1500 eV in K2 1 a.u. even at 1500 eV. It is also observed that the minimum position of the generalized oscillator strength of the vibronic state shifts toward the larger squared momentum transfer with the increasing vibrational quantum number. By extrapolating the generalized oscillator strength to the zero momentum transfer, the optical oscillator strength of the AA2″1 state has been obtained, which gives an independent cross check to the previous results. The integral cross sections of the AA2″1 state have been obtained systematically from the threshold to 5000 eV with the aid of the BE-scaling method.

7 citations

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TL;DR: In this paper, the generalized oscillator strengths of the valence-shell excitations from the ground state to 3p5(4s, 4s', 4p, 4p', 3d, 3d', 5p, 5p', 5s,4d) of argon have been determined at an incident electron energy of 1500 eV and an energy resolution about 90 meV.

Abstract: The generalized oscillator strengths of the valence-shell excitations from the ground state to 3p5(4s, 4s', 4p, 4p', 3d, 3d', 5p, 5p', 5s, 4d) of argon have been determined at an incident electron energy of 1500 eV and an energy resolution about 90 meV. The accuracy of the present generalized oscillator strengths is improved by the adopted relative flow technique. The comprehensive comparison of the present results with the previous experimental and theoretical ones shows that the first Born approximation is satisfied in the lower squared momentum transfer region for the electric dipole excitations, while the deviations from the prediction of the first Born approximation and the inelastic X-ray scattering measurements near the minimum and in the larger K2 region are obvious, which can be attributed to the failure of the first Born approximation in this K2 region. The invalidity of the first Born approximation has also been observed for the electric monopole transitions even at a high impact electron energy of 2500 eV.

7 citations

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TL;DR: In this paper, the authors compare the ICSs determined by high-energy electron scattering with the existing experiments at low and intermediate energies and theories, where the present experiment eliminated the errors from the spectral deconvolution in low-energy measurements.

Abstract: Understanding the role of inelastic electron scattering in water is of fundamental importance in various fields ranging from atmospheric chemistry to radiation biology. The lack of accurate excitation cross sections for water results in a large uncertainty, for example, in the track structure simulation for modeling radiation damage to DNA. The large differences of the integral cross sections (ICSs) for the optical-allowed excitations ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{A}}^{1}{B}_{1}$ and ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{B}}^{1}{A}_{1}$ of ${\mathrm{H}}_{2}\mathrm{O}$ among experiments and theories have been maintaining for decades. To resolve this issue, by combining the ab initio calculation with the electron correlation being taken into account accurately, we compare the ICSs determined by high-energy electron scattering with the existing experiments at low and intermediate energies and theories, where the present experiment eliminated the errors from the spectral deconvolution in low-energy measurements. Our work provides a recommendation for the ICSs of the two excitations from thresholds up to several keV, and suggests the existing selected ICSs for ${\mathrm{H}}_{2}\mathrm{O}$ be revised for accurate modeling radiation effects in biological matter and describing the transport properties of electrons in aqueous systems.

6 citations

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TL;DR: A series of highly accurate excited-state properties obtained using high-order coupled-cluster calculations performed with a series of diffuse containing basis sets, and extensive comparisons with experimental values are presented.

Abstract: This work presents a series of highly accurate excited-state properties obtained using high-order coupled-cluster (CC) calculations performed with a series of diffuse containing basis sets, and extensive comparisons with experimental values. Indeed, we have computed the main ground-to-excited transition property, the oscillator strength, and the ground- and excited-state dipole moments, considering 13 small molecules (hydridoboron, hydrogen chloride, water, hydrogen sulfide, boron fluoride, carbon monoxide, dinitrogen, ethylene, formaldehyde, thioformaldehyde, nitroxyl, fluorocarbene, and silylidene). We systematically include corrections up to the quintuple (CCSDTQP) in the CC expansion and extrapolate to the complete basis set limit. When comparisons with experimental measurements are possible, that is, when a number of consistent experimental data can be found, theory typically provides values falling within the experimental error bar for the excited-state properties. Besides completing our previous studies focused on transition energies [J. Chem. Theory Comput. 14 (2018) 4360-4379, ibid. 15 (2019) 1939-1956, ibid. 16 (2020) 1711-1741, and ibid. 16 (2020) 3720-3736], this work also provides ultra-accurate dipoles and oscillator strengths that could be employed for future theoretical benchmarks.

28 citations

01 Jan 1975

19 citations

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TL;DR: In this paper, the authors review newly developed experimental methods for NRIXS, together with its characteristics and various applications, with emphasis on the new insights into excitation mechanism and other new information revealed by this technique.

12 citations

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TL;DR: In this paper , a deep variational quantum Monte Carlo (QMC) approach is proposed to compute the ground and low-lying excited states of electronic systems using deep neural networks.

Abstract: Abstract Obtaining accurate ground and low-lying excited states of electronic systems is crucial in a multitude of important applications. One ab initio method for solving the Schrödinger equation that scales favorably for large systems is variational quantum Monte Carlo (QMC). The recently introduced deep QMC approach uses ansatzes represented by deep neural networks and generates nearly exact ground-state solutions for molecules containing up to a few dozen electrons, with the potential to scale to much larger systems where other highly accurate methods are not feasible. In this paper, we extend one such ansatz (PauliNet) to compute electronic excited states. We demonstrate our method on various small atoms and molecules and consistently achieve high accuracy for low-lying states. To highlight the method’s potential, we compute the first excited state of the much larger benzene molecule, as well as the conical intersection of ethylene, with PauliNet matching results of more expensive high-level methods.

11 citations

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TL;DR: The generalized oscillator strengths of the valence-shell excitations of HCl have been measured at an incident electron energy of 1500 eV and an energy resolution of 70 meV, and their momentum transfer dependence behaviors have been elucidated.

Abstract: The oscillator strengths and integral cross sections of the valence-shell excitations of HCl have significant applications in the studies of planetary atmospheres and interstellar gases. In the present work, the generalized oscillator strengths of the valence-shell excitations of HCl have been measured at an incident electron energy of 1500 eV and an energy resolution of 70 meV, and their momentum transfer dependence behaviors have been elucidated. It is observed that the generalized oscillator strength ratios of the b3Π1(ν' = 0) state to the C1Π(ν' = 0) state are a constant and independent of the squared momentum transfer, and this typical behavior in the momentum space is explained by the intraconfiguration mixing of the b3Π1 and C1Π states due to the spin-orbital interaction. The optical oscillator strengths of the valence-shell excitations have been obtained by extrapolating the generalized oscillator strengths to the limit of zero squared momentum transfer. The present optical oscillator strengths give an independent cross-check to the previous experimental and theoretical results, and it is found that most of the photoabsorption measurements are limited by the line saturation effect. The integral cross sections of the valence-shell excitations of HCl have been obtained systematically from the threshold to 5000 eV with the aid of the BE-scaling method.

8 citations