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Atomic and Molecular Physics|20 Article(s)
Probing the Structure of Asymmetric Planar Molecules Using Odd-Even High Harmonics
Shujuan Yu, Zhuqin Liu, Yanfeng Liu, and Yanpeng Li
The generation of high-order harmonics from planar molecules H32+ with different molecular configurations is studied using the numerical solution of the time-dependent Schr?dinger equation. The results show that planar molecules H32+ emit both odd and even harmonics, and the relative yields of odd and even harmonics are sensitive to orientation angles and molecular configuration. A simple method is proposed, based on the above results, to detect the position of atomic nucleus via odd and even high-order harmonic spectra. Bond lengths and angles from oriented asymmetric planar molecules can be reconstructed using odd-even harmonics at different angles. Meanwhile, probing the polycentric molecular structure in attoseconds using a high-order harmonic spectrum is helpful. The generation of high-order harmonics from planar molecules H32+ with different molecular configurations is studied using the numerical solution of the time-dependent Schr?dinger equation. The results show that planar molecules H32+ emit both odd and even harmonics, and the relative yields of odd and even harmonics are sensitive to orientation angles and molecular configuration. A simple method is proposed, based on the above results, to detect the position of atomic nucleus via odd and even high-order harmonic spectra. Bond lengths and angles from oriented asymmetric planar molecules can be reconstructed using odd-even harmonics at different angles. Meanwhile, probing the polycentric molecular structure in attoseconds using a high-order harmonic spectrum is helpful.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2023
- Vol. 60, Issue 1, 0102002 (2023)
Study on Geometric Structures and Electronic and Thermodynamic Properties of CoSi16- and Co2Si322- Clusters
Jiaxiu Li, Jiangshui Guo, Lin Cheng, Mengjiao Guo, Ziang Wang, Chenggang Li, and Yingqi Cui
Doping of silicon clusters with transition metals can enhance the stability of such clusters and confer many peculiar physical and chemical properties. Therefore, this method occupies an important position in the fields of new energy and materials science. Herein, we report the geometric structures as well as electronic and thermodynamic properties of CoSi16- and Co2Si322- clusters using the particle swarm optimization algorithm CALYPSO searching method and density functional theory. Results indicate that the lowest structures of the CoSi16- and Co2Si322- clusters exhibit the highly symmetric D2d and D2h point structures, respectively, in which the Co atom is completely encapsulated in Si cages. Based on these structures, various electronic properties, including the magnetic properties and bond order, are systemically evaluated. In addition, the photoelectron spectra, infrared spectra, and Raman spectra are recorded to identify the main characteristic peaks of the two systems. Finally, the thermodynamic properties of the two systems are investigated. Moreover, the temperature dependence of Cv and S for the CoSi16- and Co2Si322- clusters is discussed. Doping of silicon clusters with transition metals can enhance the stability of such clusters and confer many peculiar physical and chemical properties. Therefore, this method occupies an important position in the fields of new energy and materials science. Herein, we report the geometric structures as well as electronic and thermodynamic properties of CoSi16- and Co2Si322- clusters using the particle swarm optimization algorithm CALYPSO searching method and density functional theory. Results indicate that the lowest structures of the CoSi16- and Co2Si322- clusters exhibit the highly symmetric D2d and D2h point structures, respectively, in which the Co atom is completely encapsulated in Si cages. Based on these structures, various electronic properties, including the magnetic properties and bond order, are systemically evaluated. In addition, the photoelectron spectra, infrared spectra, and Raman spectra are recorded to identify the main characteristic peaks of the two systems. Finally, the thermodynamic properties of the two systems are investigated. Moreover, the temperature dependence of Cv and S for the CoSi16- and Co2Si322- clusters is discussed.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2023
- Vol. 60, Issue 1, 0102001 (2023)
Theoretical Study on Laser Cooling of Strontium Chloride Molecules
Yulong Han, Dong Cheng, Hui Sun, Jinfang Sun, Baohang Zhou, and Eryin Feng
The potential energy curves for seven Λ-S electronic states (X2Σ+, B2Σ+, C2Δ, F2Σ+, A2Π, D2Π, and E2Π) of strontium chloride (SrCl) molecule are investigated using the multireference configuration interaction method (MRCI). Davidson correction (+Q), core-valence correction, and spin-orbit coupling effect are considered in the calculation. Based on the obtained potential energy curves of Λ-S states, the vibration energy levels, wave functions, and spectroscopic parameters are determined by solving the Schrödinger equation using the discrete position presentation method. The calculated values agree substantially with experimental and theoretical values. Additionally, the transition dipole moments, Franck-Condon factors, and radiative lifetime of the SrCl molecule are explored. Due to the significant diagonal distribution of the Franck-Condon factors (f00=0.96959) and short radiative lifetimes (τ=31.05 ns) of the A2Π (ν′=0) →X2Σ+(ν″=0) transition, the SrCl molecules are suitable for rapid laser cooling. Therefore, this study presents a three-laser scheme for laser cooling of SrCl molecules. The calculated pump and repump wavelengths of the laser-driven cycling are668.2 nm (λ00), 682.0 nm (λ01), and 681.5 nm (λ12). The potential energy curves for seven Λ-S electronic states (X2Σ+, B2Σ+, C2Δ, F2Σ+, A2Π, D2Π, and E2Π) of strontium chloride (SrCl) molecule are investigated using the multireference configuration interaction method (MRCI). Davidson correction (+Q), core-valence correction, and spin-orbit coupling effect are considered in the calculation. Based on the obtained potential energy curves of Λ-S states, the vibration energy levels, wave functions, and spectroscopic parameters are determined by solving the Schrödinger equation using the discrete position presentation method. The calculated values agree substantially with experimental and theoretical values. Additionally, the transition dipole moments, Franck-Condon factors, and radiative lifetime of the SrCl molecule are explored. Due to the significant diagonal distribution of the Franck-Condon factors (f00=0.96959) and short radiative lifetimes (τ=31.05 ns) of the A2Π (ν′=0) →X2Σ+(ν″=0) transition, the SrCl molecules are suitable for rapid laser cooling. Therefore, this study presents a three-laser scheme for laser cooling of SrCl molecules. The calculated pump and repump wavelengths of the laser-driven cycling are668.2 nm (λ00), 682.0 nm (λ01), and 681.5 nm (λ12).
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2022
- Vol. 59, Issue 7, 0702001 (2022)
Molecular Structure and Dissociation Characteristic of 4-Bromophenol Under External Electric Fields
Huan An, Haokui Yan, Mei Xiang, Bumaliya Abulimiti, Xingchen Wang, and Jingyan Zheng
Density functional theory (DFT) and time-dependent density functional theory (TDDFT) at the B3LYP/6-311+G(d, p) level were used to calculate and optimize the physical characteristics of 4-bromophenol under the different electric fields, including the bond length, bond angle, total energy, dipole moment, energy gap, infrared spectrum, dissociation properties, and excited state. The results revealed a significant change in the molecular structure of 4-bromophenol under an external electric field (0-0.03 a.u.). The molecular C—Br bond length, O—H bond length, and dipole moment increased gradually with increasing external electric field, while the C—O bond length, total energy, and energy gap decreased gradually. The four absorption peaks of the molecular infrared spectrum showed a red shift. Simultaneously, the first 10 excited states also showed a red shift. When the external electric field intensity was 0.03 a.u., the potential barrier disappeared, and molecular dissociation was observed. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) at the B3LYP/6-311+G(d, p) level were used to calculate and optimize the physical characteristics of 4-bromophenol under the different electric fields, including the bond length, bond angle, total energy, dipole moment, energy gap, infrared spectrum, dissociation properties, and excited state. The results revealed a significant change in the molecular structure of 4-bromophenol under an external electric field (0-0.03 a.u.). The molecular C—Br bond length, O—H bond length, and dipole moment increased gradually with increasing external electric field, while the C—O bond length, total energy, and energy gap decreased gradually. The four absorption peaks of the molecular infrared spectrum showed a red shift. Simultaneously, the first 10 excited states also showed a red shift. When the external electric field intensity was 0.03 a.u., the potential barrier disappeared, and molecular dissociation was observed.
Laser & Optoelectronics Progress
- Publication Date: Feb. 10, 2022
- Vol. 59, Issue 3, 0302001 (2022)
Theoretical Study of High-Order Harmonic Generation from Acceptor-Doped Semiconductor
Yanfeng Wang, and Xiangyang Miao
We theoretically investigate the high-order harmonic generation from acceptor-doped semiconductors by numerically solving the one-dimensional time-dependent Schr?dinger equation based on the single electron approximation. The results show that the harmonic efficiency of the second plateau from acceptor-doped semiconductors is about three to four orders of magnitude higher than those from undoped semiconductors. Theoretical analysis shows that doping changes the energy-band structure of the semiconductor, narrows the band gap between the valence band and the first conduction band, and between the first conduction band and the second conduction band. Then it is easier for electrons to tunnel into the higher conduction band, and the electron population of the high conduction band is increased, thus the harmonic efficiency of the second plateau is improved. We theoretically investigate the high-order harmonic generation from acceptor-doped semiconductors by numerically solving the one-dimensional time-dependent Schr?dinger equation based on the single electron approximation. The results show that the harmonic efficiency of the second plateau from acceptor-doped semiconductors is about three to four orders of magnitude higher than those from undoped semiconductors. Theoretical analysis shows that doping changes the energy-band structure of the semiconductor, narrows the band gap between the valence band and the first conduction band, and between the first conduction band and the second conduction band. Then it is easier for electrons to tunnel into the higher conduction band, and the electron population of the high conduction band is increased, thus the harmonic efficiency of the second plateau is improved.
Laser & Optoelectronics Progress
- Publication Date: Jul. 10, 2022
- Vol. 59, Issue 13, 1302001 (2022)
Transient Absorption Properties of Rydberg Atom Driven by Two Pulsed Laser Fields
Guiyin Zhang, Xuan Zhao, Songtao Li, and Haiming Zheng
The transient absorption properties of Rydberg atoms driven by two pulsed laser fields are investigated herein on the basis of the theory of density matrix equation, which describes the interaction of photon and material. It is found that owing to the weak coupling field, the probe absorption first increases to the maximum value and then decreases monotonically to zero with time. The maximum value of the probe absorption increases with an increase in Rabi frequency until the largest value is obtained. Then, it decreases gradually and the absorption with time presents the character of oscillation at the same time. When the coupling field's Rabi frequency is appropriate, the phenomenon of negative absorption occurs. The analysis of the evolution of population and the coherent term with time reveals that the coherent term caused by the influence of the coupling and probe field results in a negative absorption. The transient absorption properties of Rydberg atoms driven by two pulsed laser fields are investigated herein on the basis of the theory of density matrix equation, which describes the interaction of photon and material. It is found that owing to the weak coupling field, the probe absorption first increases to the maximum value and then decreases monotonically to zero with time. The maximum value of the probe absorption increases with an increase in Rabi frequency until the largest value is obtained. Then, it decreases gradually and the absorption with time presents the character of oscillation at the same time. When the coupling field's Rabi frequency is appropriate, the phenomenon of negative absorption occurs. The analysis of the evolution of population and the coherent term with time reveals that the coherent term caused by the influence of the coupling and probe field results in a negative absorption.
Laser & Optoelectronics Progress
- Publication Date: Jun. 10, 2022
- Vol. 59, Issue 11, 1102001 (2022)
Atomic Dynamic Interference in Chirped Laser Fields with Different Polarizations
Shun Wang, Shahab Ullah Khan, Xiaoqing Tian, and Huibin Sun
By accurately solving the full-dimensional time-dependent Schr?dinger equation (TDSE), the dynamic interference effects in the ionization of atomic hydrogen by chirped laser pulses with different polarizations are numerically studied. The emphasis is put on the influences of the chirp parameters on the dynamic interference patterns of the photoelectron energy spectra. Numerical results show that the increase of the chirp will cause the suppression of dynamic interference pattern in three polarization cases; for any chirp parameter, the interference subpeaks show a rightward shift when the ellipticity of the pulse increases; for any chirp parameter, the dynamic interference pattern will disappear when the laser pulse is up to 30 fs, indicating that the previously reported calculation of one-dimensional TDSE cannot accurately describe the real physical process. By accurately solving the full-dimensional time-dependent Schr?dinger equation (TDSE), the dynamic interference effects in the ionization of atomic hydrogen by chirped laser pulses with different polarizations are numerically studied. The emphasis is put on the influences of the chirp parameters on the dynamic interference patterns of the photoelectron energy spectra. Numerical results show that the increase of the chirp will cause the suppression of dynamic interference pattern in three polarization cases; for any chirp parameter, the interference subpeaks show a rightward shift when the ellipticity of the pulse increases; for any chirp parameter, the dynamic interference pattern will disappear when the laser pulse is up to 30 fs, indicating that the previously reported calculation of one-dimensional TDSE cannot accurately describe the real physical process.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2022
- Vol. 59, Issue 1, 0102001 (2022)
Power-Frequency Electric Field Measurement Based on AC-Stark Effect of Rydberg Atoms
Wei Li, Chungang Zhang, Hao Zhang, Mingyong Jing, and Linjie Zhang
The 42D Rydberg atom is prepared in cesium vapor at room temperature, and the power-frequency electric field is measured based on the electromagnetically induced transparency spectrum of Rydberg atom. The 42D Rydberg atom is prepared by two-photon excitation, and the stepped electromagnetically induced transparency spectrum is obtained by changing the coupling frequency. The relationship between the spectral frequency shift and splitting of Rydberg atom under radio frequency(RF) electric field and the amplitude and frequency of RF electric field is studied. By modulating the amplitude of power-frequency electric field to RF electric field, the measurement of power-frequency electric field intensity and frequency is realized. Research results has important reference value and significance for online traceable measurement of power-frequency electric field. The 42D Rydberg atom is prepared in cesium vapor at room temperature, and the power-frequency electric field is measured based on the electromagnetically induced transparency spectrum of Rydberg atom. The 42D Rydberg atom is prepared by two-photon excitation, and the stepped electromagnetically induced transparency spectrum is obtained by changing the coupling frequency. The relationship between the spectral frequency shift and splitting of Rydberg atom under radio frequency(RF) electric field and the amplitude and frequency of RF electric field is studied. By modulating the amplitude of power-frequency electric field to RF electric field, the measurement of power-frequency electric field intensity and frequency is realized. Research results has important reference value and significance for online traceable measurement of power-frequency electric field.
Laser & Optoelectronics Progress
- Publication Date: Sep. 10, 2021
- Vol. 58, Issue 17, 1702002 (2021)
Fifth-Order Nonlinear Effects by Electromagnetical Induced Enhancement
Shudi Mei, Xinyi Zhang, Guoguo Xin, and Yingjie Du
In order to extend the measurement of the nonlinear effect intensity to the fifth-order nonlinear, the fifth-order nonlinear effect in the electromagnetically induced transparency system is studied theoretically. The research results show that the quantum coherence effect greatly enhances the nonlinear effects of electromagnetically induced transparency system, including susceptibility of third-order nonlinear which can simulate Raman scattering and four-wave mixing, fifth-order nonlinear susceptibility with two completely different nonlinear absorption and dispersion.The fifth-order cross nonlinearity of the nonlinear absorption excites the four-photon absorption and the fifth-order cross nonlinearity of the nonlinear gain excites the super Raman scattering. The fifth-order cross nonlinearity of the electric polarization of the nonlinear absorption excites the six-wave mixing. In order to extend the measurement of the nonlinear effect intensity to the fifth-order nonlinear, the fifth-order nonlinear effect in the electromagnetically induced transparency system is studied theoretically. The research results show that the quantum coherence effect greatly enhances the nonlinear effects of electromagnetically induced transparency system, including susceptibility of third-order nonlinear which can simulate Raman scattering and four-wave mixing, fifth-order nonlinear susceptibility with two completely different nonlinear absorption and dispersion.The fifth-order cross nonlinearity of the nonlinear absorption excites the four-photon absorption and the fifth-order cross nonlinearity of the nonlinear gain excites the super Raman scattering. The fifth-order cross nonlinearity of the electric polarization of the nonlinear absorption excites the six-wave mixing.
Laser & Optoelectronics Progress
- Publication Date: Sep. 10, 2021
- Vol. 58, Issue 17, 1702001 (2021)
Multipath Conversion and Interference Effect of Ultracold Bosonic Heteronuclear Tetra-Atomic Molecule
Fuquan Dou, Jiahui Zhang, Jing Yang, and Dan Hu
In this study, we investigated the single-path and multipath conversions of ultracold bosonic heteronuclear tetra-atomic molecules using the generalized stimulated Raman adiabatic passage technique. First, we established a mean-field model and obtained the corresponding dark state solutions and two-photon resonance conditions. Next, we compared the molecule conversion dynamics of the single-path and multipath cases and found that constructive interference effects existed in the multipath cases; this could increase the molecular conversion rate. In particular, for the three-path scheme, the interference effect was obvious and the conversion rate was high. We further studied the influence of external field parameters on the conversion rate of the multipath scheme by varying the pulse intensity and found that the influence had two sides: constructive and destructive interference, respectively, which increased and decreased the conversion rate of molecules. In this study, we investigated the single-path and multipath conversions of ultracold bosonic heteronuclear tetra-atomic molecules using the generalized stimulated Raman adiabatic passage technique. First, we established a mean-field model and obtained the corresponding dark state solutions and two-photon resonance conditions. Next, we compared the molecule conversion dynamics of the single-path and multipath cases and found that constructive interference effects existed in the multipath cases; this could increase the molecular conversion rate. In particular, for the three-path scheme, the interference effect was obvious and the conversion rate was high. We further studied the influence of external field parameters on the conversion rate of the multipath scheme by varying the pulse intensity and found that the influence had two sides: constructive and destructive interference, respectively, which increased and decreased the conversion rate of molecules.
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 2021
- Vol. 58, Issue 11, 1102001 (2021)
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