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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For selected: Download citations EndNote Ris BibTeX Toggle thumbnails Select Elliptically polarized high-order harmonic generation in nitrogen molecules with cross-linearly polarized two-color laser fields Chunyang Zhai(翟春洋), Yinmeng Wu(吴银梦), Lingling Qin(秦玲玲), Xiang Li(李翔), Luke Shi(史璐珂), Ke Zhang(张可), Shuaijie Kang(康帅杰), Zhengfa Li(李整法), Yingbin Li(李盈傧), Qingbin Tang(汤清彬), and Benhai Yu(余本海) Chin. Phys. B, 2023, 32 (7): 073301.   DOI: 10.1088/1674-1056/acad70 Abstract （167）   HTML （1）    PDF （1606KB）（127）       Knowledge map    Circularly and elliptically polarized high-order harmonics have unique advantages when used in studying the chiral and magnetic features of matter. Here, we studied the polarization properties of high-order harmonics generated from alignment nitrogen molecules driven by cross-linearly polarized two-color laser fields. Through adjusting various laser parameters and targets, such as the relative phase, the crossing angle, the intensity ratio of the driving fields, and the molecular alignment angle, we obtained highly elliptically polarized high-order harmonics with the same helicity in a wide spectral range. This provides a possible effective way to generate elliptically polarized attosecond pulses. Finally, we showed the probability of controlling the spectral range of elliptically polarized harmonics. Select Saturated absorption spectrum of cesium micrometric-thin cell with suppressed crossover spectral lines Junlong Han(韩俊龙), Bowen Wang(王博闻), Junhe Zheng(郑俊鹤), Shuyuan Chen(陈书源),Wei Xiao(肖伟), Teng Wu(吴腾), Hong Guo(郭弘), and Xiang Peng(彭翔) Chin. Phys. B, 2023, 32 (7): 073201.   DOI: 10.1088/1674-1056/acc802 Abstract （140）   HTML （3）    PDF （1091KB）（123）       Knowledge map    Micrometric-thin cells (MCs) with alkali vapor atoms have been valuable for research and applications of hyperfine Zeeman splitting and atomic magnetometers under strong magnetic fields. We theoretically and experimentally study the saturated absorption spectra using a 100-μ cesium MC, where the pump and probe beams are linearly polarized with mutually perpendicular polarizations, and the magnetic field is along the pump beam. Because of the distinctive thin chamber of the MC, crossover spectral lines in saturated absorption spectra are largely suppressed leading to clear splittings of hyperfine Zeeman transitions in experiments, and the effect of spatial magnetic field gradient is expected to be reduced. A calculation method is proposed to achieve good agreements between theoretical calculations and experimental results. This method successfully explains the suppression of crossover lines in MCs, as well as the effects of magnetic field direction, propagation and polarization directions of the pump/probe beam on saturated absorption spectrum. The saturated absorption spectrum with suppressed crossover lines is used for laser frequency stabilization, which may provide the potential value of MCs for high spatial resolution strong-field magnetometry with high sensitivity. Select Electric field intensity measurement by using doublet electromagnetically induced transparency of cold Rb Rydberg atoms Ting Gong(宫廷), Shuai Shi(师帅), Zhonghua Ji(姬中华), Guqing Guo(郭古青), Xiaocong Sun(孙小聪), Yali Tian(田亚莉), Xuanbing Qiu(邱选兵), Chuanliang Li(李传亮), Yanting Zhao(赵延霆), and Suotang Jia(贾锁堂) Chin. Phys. B, 2023, 32 (10): 103202.   DOI: 10.1088/1674-1056/acf120 Abstract （118）   HTML （0）    PDF （740KB）（135）       Knowledge map    We demonstrate a simple method to measure electric field intensity by using doublet electromagnetically induced transparency (EIT) spectra of cold Rb Rydberg atoms, where the frequency of the coupling laser does not need to be locked. Based on the Stark splitting of the Rb Rydberg state, 10D3/2, under electric fields and the corresponding calculated polarizabilities, the real electric field intensity is calculated using the difference in radio-frequency diffraction between two acousto-optic modulators, which acts as a frequency criterion that allows us to measure the electrical field without locking the coupling laser. The value measured by this simple method shows a good agreement with our previous work [Opt. Express 29 1558 (2021)] where the frequency of the coupling laser needs to be locked with an additional EIT spectrum based on atom vapor and a proportional-integral-differential feedback circuit. Our presented method can also be extended to the measurement of electric field based on hot Rydberg atom vapor, which has application in industry. Select Lifetime measurement of the 3d9 2D3/2 metastable level in Mo15+ at an electron beam ion trap Jialin Liu(刘佳林), Yintao Wang(王银涛), Bingsheng Tu(屠秉晟), Liangyu Huang(黄良玉), Ran Si(司然), Jiguang Li(李冀光), Mingwu Zhang(张明武), Yunqing Fu(傅云清), Yaming Zou(邹亚明), and Ke Yao(姚科) Chin. Phys. B, 2023, 32 (10): 103201.   DOI: 10.1088/1674-1056/acf121 Abstract （117）   HTML （0）    PDF （1052KB）（44）       Knowledge map    An experimental measurement of the lifetime of $3\rm d^9$ $^2{\rm D}_{3/2}$ metastable level in Mo$^{15+}$ is reported in this work. The Mo$^{15+}$ ions are produced and trapped in an electron beam ion trap with a magnetic field of 0.65 T. The decay photons emitted from $3\rm d^9$ $^2{\rm D}_{3/2}$ level are subsequently recorded via a cooled photomultiplier tube. Through meticulous scrutiny of potential systematic uncertainties affecting the measurement outcomes, we have determined the lifetime of Mo$^{15+}$ $3\rm d^9$ $^2{\rm D}_{3/2}$ metastable level to be 2.83(22) ms. The experimental result provides a clear distinguishment from existing calculations based on various theoretical approaches. Select Effect of aggregation on thermally activated delayed fluorescence and ultralong organic phosphorescence: QM/MM study Qun Zhang(张群), Xiaofei Wang(王晓菲), Zhimin Wu(吴智敏), Xiaofang Li(李小芳), Kai Zhang(张凯), Yuzhi Song(宋玉志), Jianzhong Fan(范建忠), Chuan-Kui Wang(王传奎), and Lili Lin(蔺丽丽) Chin. Phys. B, 2023, 32 (10): 103301.   DOI: 10.1088/1674-1056/acb75d Abstract （110）   HTML （0）    PDF （5824KB）（10）       Knowledge map    Aggregation-induced thermally activated delayed fluorescence (TADF) phenomena have attracted extensive attention recently. In this paper, several theoretical models including monomer, dimer, and complex are used for the explanation of the luminescent properties of ($R$)-5-(9H-carbazol-9-yl)-2-(1,2,3,4-tetrahydronaphthalen-1-yl)isoindoline-1,3-dione (($R$)-ImNCz), which was recently reported [$Chemical Engineering Journal$ 418 129167 (2021)]. The polarizable continuum model (PCM) and the combined quantum mechanics and molecular mechanics (QM/MM) method are adopted in simulation of the property of the molecule in the gas phase, solvated in acetonitrile and in aggregation states. It is found that large spin--orbit coupling (SOC) constants and a smaller energy gap between the first singlet excited state and the first triplet excited state ($\Delta E_{\rm st}$) in prism-like single crystals (SC$_{\rm p}$-form) are responsible for the TADF of ($R$)-lmNCz, while no TADF is found in block-like single crystals (SC$_{\rm b}$-form) with a larger $\Delta E_{\rm st}$. The multiple ultralong phosphorescence (UOP) peaks in the spectrum are of complex origins, and they are related not only to ImNCz but also to a minor amount of impurities (ImNBd) in the crystal prepared in the laboratory. The dimer has similar phosphorescence emission wavelengths to the ($R$)-lmNCz-SC$_{\rm p}$ monomers. The complex composed of ($R$)-lmNCz and ($R$)-lmNBd contributes to the phosphorescent emission peak at about 600 nm, and the phosphorescent emission peak at about 650 nm is generated by ($R$)-lmNBd. This indicates that the impurity could also contribute to emission in molecular crystals. The present calculations clarify the relationship between the molecular aggregation and the light-emitting properties of the TADF emitters and will therefore be helpful for the design of potentially more useful TADF emitters. Select High-order harmonic generation of ZnO crystals in chirped and static electric fields Ling-Yu Zhang(张玲玉), Yong-Lin He(何永林), Zhuo-Xuan Xie(谢卓璇), Fang-Yan Gao(高芳艳), Qing-Yun Xu(徐清芸), Xin-Lei Ge(葛鑫磊), Xiang-Yi Luo(罗香怡), and Jing Guo(郭静) Chin. Phys. B, 2024, 33 (1): 013102.   DOI: 10.1088/1674-1056/acfa89 Abstract （107）   HTML （2）    PDF （14461KB）（128）       Knowledge map    High harmonic generation in ZnO crystals under chirped single-color field and static electric field are investigated by solving the semiconductor Bloch equation (SBE). It is found that when the chirp pulse is introduced, the interference structure becomes obvious while the harmonic cutoff is not extended. Furthermore, the harmonic efficiency is improved when the static electric field is included. These phenomena are demonstrated by the classical recollision model in real space affected by the waveform of laser field and inversion symmetry. Specifically, the electron motion in k-space shows that the change of waveform and the destruction of the symmetry of the laser field lead to the incomplete X-structure of the crystal-momentum-resolved (k-resolved) inter-band harmonic spectrum. Furthermore, a pre-acceleration process in the solid four-step model is confirmed. Select Electron vortices generation of photoelectron of H2+ by counter-rotating circularly polarized attosecond pulses Haojing Yang(杨浩婧), Xiaoyu Liu(刘晓煜), Fengzheng Zhu(朱风筝), Liguang Jiao(焦利光), and Aihua Liu(刘爱华) Chin. Phys. B, 2024, 33 (1): 013303.   DOI: 10.1088/1674-1056/ad011a Abstract （105）   HTML （0）    PDF （1733KB）（65）       Knowledge map    Molecular-frame photoelectron momentum distributions (MF-PMDs) of an H2+ molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrödinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counter-rotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distance-dependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs. Select Role of excited states in helium-like ions on high-order harmonic generation Jiang-Hua Luo(罗江华) and Jia-Jun Xiao(肖佳俊) Chin. Phys. B, 2023, 32 (11): 113201.   DOI: 10.1088/1674-1056/ace317 Abstract （99）   HTML （1）    PDF （896KB）（37）       Knowledge map    We theoretically investigate high-order harmonic generation (HHG) of helium (He), lithium cation (Li+), and beryllium dication (Be2+) using the time-dependent Hartree-Fock method to solve the three-dimensional time-dependent Schrödinger equation. It is found that the intensity of the HHG increases significantly from a certain harmonic order below the ionization threshold, and the initial position of the enhancement does not depend on the intensity or the wavelength of the driving laser field. Further analysis shows that excited states play an important role on this enhancement, consistent with the excited-state tunneling mechanism [Phys. Rev. Lett. 116 123901 (2016)]. Our results unambiguously show that excited-state tunneling is essential for understanding the enhancement of HHG. Accordingly, a four-step model is herein proposed to illustrate the multiphoton excitation effect in helium-like ions, which enriches the physics of HHG enhancement. Select Internal collision double ionization of molecules driven by co-rotating two-color circularly polarized laser pulses Xue-Feng Li(李雪峰), Yue Qiao(乔月), Dan Wu(吴丹), Rui-Xian Yu(蔚瑞贤), Ji-Gen Chen(陈基根), Jun Wang(王俊), Fu-Ming Guo(郭福明), and Yu-Jun Yang(杨玉军) Chin. Phys. B, 2024, 33 (1): 013302.   DOI: 10.1088/1674-1056/acf5d8 Abstract （97）   HTML （0）    PDF （1316KB）（85）       Knowledge map    The double ionization process of molecules driven by co-rotating two-color circularly polarized fields is investigated with a three-dimensional classical ensemble model. Numerical results indicate that a considerable part of the sequential double ionization (DI) events of molecules occur through internal collision double ionization (ICD), and the ICD recollision mechanism is significantly different from that in non-sequential double ionization (NSDI). By analyzing the results of internuclear distances R=5 a.u. and 2 a.u., these two recollision mechanisms are studied in depth. It is found that the dynamic behaviors of the recollision mechanisms of NSDI and ICD are similar. For NSDI, the motion range of electrons after the ionization is relatively large, and the electrons will return to the core after a period of time. In the ICD process, electrons will rotate around the parent ion before ionization, and the distance of the electron motion is relatively small. After a period of time, the electrons will come back to the core and collide with another electron. Furthermore, the molecular internuclear distance has a significant effect on the electron dynamic behavior of the two ionization mechanisms. This study will help to understand the multi-electron ionization process of complex systems. Select Revising the H216O line-shape parameters around 1.1 μm based on the speed-dependent Nelkin-Ghatak profile and the Hartmann-Tran profile Hui Zhang(张惠), Jianjie Zheng(郑健捷), Qiang Liu(刘强), Wenyue Zhu(朱文越), Xianmei Qian(钱仙妹), Guisheng Jiang(江贵生), Shenlong Zha(查申龙), Qilei Zhang(张启磊), and Hongliang Ma(马宏亮) Chin. Phys. B, 2023, 32 (12): 123301.   DOI: 10.1088/1674-1056/acc7f5 Abstract （95）   HTML （0）    PDF （1503KB）（17）       Knowledge map    Accurate spectroscopic data for H216O in the 1.1 μ m region are particularly important for the study of Earth's atmosphere. The pure water vapor molecular spectra were measured based on direct laser absorption spectroscopy using a narrow line-width external cavity diode laser combined with a high-precision Fabry-Pérot etalon. A total of 31 H216O transitions were studied for the first time by using the speed-dependent Nelkin-Ghatak profile and the Hartmann-Tran profile. From an accurate line-shape analysis, we obtained the line intensities and the self-broadening coefficients, and they are compared with the available data reported in the HITRAN 2016 database and the HITRAN 2020 database. Finally, we obtained information on the influence of Dicke narrowing, as well as the correlations between Dicke narrowing and speed dependence, and of speed-dependent effects. Select Mixed-field effect at the hyperfine level of 127I79Br in its rovibronic ground state: Toward field manipulation of cold molecules Zhengbin Bao(包正斌), Defu Wang(王得富), Xuping Shao(邵旭萍),Yunxia Huang(黄云霞), and Xiaohua Yang(杨晓华) Chin. Phys. B, 2023, 32 (12): 123302.   DOI: 10.1088/1674-1056/ace61c Abstract （88）   HTML （0）    PDF （901KB）（14）       Knowledge map    The mixed-field effect at the hyperfine level of the rovibronic ground state of the 127I79Br (X1Σ, v = 0, J = 0) molecule is computed on the J-I uncoupled basis of |JMJI1M1I2M2>, where J is the molecular total angular momentum excluding nuclear spin, MJ is the projection number of J, I1 and I2 are the nuclear spins of the iodine and bromine atoms, and M1 and M2 are the projection numbers of I1 and I2, respectively. When the two applied electric and magnetic fields are parallel, the perturbations are rare and only one perturbation is observed in a relatively large field regime in our computation range. However, when the two fields are off-parallel, the perturbations increase significantly and some sublevels show the Feshbach-like resonance phenomenon. Therefore, such sublevels transit between weak-field seeking and strong-field seeking repeatedly, which can be utilized to enhance or suppress cold molecular collision and chemical reaction rates. Such behavior of the molecular hyperfine structure in the mixed off-parallel fields may also be utilized to construct an electric-field-assisted anti-Helmholtz magnetic trap for cold molecules and to realize evaporative cooling of cold molecules (sub-mK) into the ultracold regime (μK). Select Collision off-axis position dependence of relativistic nonlinear Thomson inverse scattering of an excited electron in a tightly focused circular polarized laser pulse Yubo Wang(王禹博), Qingyu Yang(杨青屿), Yifan Chang(常一凡), Zongyi Lin(林宗熠), and Youwei Tian(田友伟) Chin. Phys. B, 2024, 33 (1): 013301.   DOI: 10.1088/1674-1056/acd921 Abstract （80）   HTML （0）    PDF （5925KB）（17）       Knowledge map    This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circularly polarized laser pulses of varying intensities. We examine the effects of the transverse ponderomotive force, specifically how the deviation angle and speed of electron motion are affected by the initial off-axis position of the electron and the peak amplitude of the laser pulse. When the laser pulse intensity is low, an increase in the electron's initial off-axis distance results in reduced spatial radiation power, improved collimation, super-continuum phenomena generation, red-shifting of the spectrum's harmonic peak, and significant symmetry in the radiation radial direction. However, in contradiction to conventional understandings, when the laser pulse intensity is relatively high, the properties of the relativistic nonlinear Thomson inverse scattering of the electron deviate from the central axis, changing direction in opposition to the aforementioned effects. After reaching a peak, these properties then shift again, aligning with the previous direction. The complex interplay of these effects suggests a greater nuance and intricacy in the relationship between laser pulse intensity, electron position, and scattering properties than previously thought. Select Structure, electronic, and nonlinear optical properties of superalkaline M3O (M = Li, Na) doped cyclo[18]carbon Xiao-Dong Liu(刘晓东), Qi-Liang Lu(卢其亮), and Qi-Quan Luo(罗其全) Chin. Phys. B, 2024, 33 (2): 023601.   DOI: 10.1088/1674-1056/ace036 Abstract （74）   HTML （0）    PDF （2801KB）（36）       Knowledge map    Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure. Superalkalis have low ionization energy. Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs. In this paper, the geometry, bonding properties, electronic structure, absorption spectrum, and nonlinear optical (NLO) properties of superalkaline $M_{3}$O ($M={\rm Li}$, Na)-doped cyclo[18]carbon were studied by using density functional theory. $M_{3}$O and the C$_{18}$ rings are not coplanar. The C$_{18}$ ring still exhibits alternating long and short bonds. The charge transfer between $M_{3}$O and C$_{18}$ forms stable [$M_{3}$O]$^{+}$[C$_{18}$]$^{-}$ ionic complexes. C$_{18}$$M_{3}$O ($M={\rm Li}$, Na) shows striking optical nonlinearity, i.e., their first- and second-order hyperpolarizability ($\beta_{\rm vec}$ and $\gamma_{\vert \vert }$) increase considerably at $\lambda = 1907$ nm and 1460 nm. Select Ab initio potential energy surface and anharmonic vibration spectrum of NF3+ Yan-Nan Chen(陈艳南), Jian-Gang Xu(徐建刚), Jiang-Peng Fan(范江鹏), Shuang-Xiong Ma(马双雄), Tian Guo(郭甜), and Yun-Guang Zhang(张云光) Chin. Phys. B, 2024, 33 (1): 013101.   DOI: 10.1088/1674-1056/ad04c6 Abstract （69）   HTML （0）    PDF （1174KB）（15）       Knowledge map    Potential energy surfaces (PESs), vibrational frequencies, and infrared spectra are calculated for NF3+ using ab initio calculations, based on UCCSD(T)/cc-pVTZ combined with vibrational configuration interaction (VCI). Based on an iterative algorithm, the surfaces (SURF) program adds automatic points to the lattice representation of the potential function, the one-dimensional and two-dimensional PESs are calculated after reaching a convergence threshold, finally the smooth image of the potential energy surface is fitted. The PESs accurately account for the interaction between the different modes, with the mode q6 symmetrical stretching vibrations having the greatest effect on the potential energy change of the whole system throughout the potential energy surface shift. The anharmonic frequencies are obtained when the VCI matrix is diagonalized. Fundamental frequencies, overtones, and combination bands of NF3+ are calculated, which generate the degenerate phenomenon between their frequencies. Finally, the calculated anharmonic frequency is used to plot the infrared spectra. Modal antisymmetric stretching ν5 and symmetric stretching ν6 exhibit a phenomenon of large-intensity borrowing. This study can provide data to support the characterization in the laboratory. Select In situ calibrated angle between the quantization axis and the propagating direction of the light field for trapping neutral atoms Rui-Jun Guo(郭瑞军), Xiao-Dong He(何晓东), Cheng Sheng(盛诚), Kun-Peng Wang(王坤鹏), Peng Xu(许鹏), Min Liu(刘敏), Jin Wang(王谨), Xiao-Hong Sun(孙晓红), Yong Zeng(曾勇), and Ming-Sheng Zhan(詹明生) Chin. Phys. B, 2024, 33 (2): 023701.   DOI: 10.1088/1674-1056/acf11d Abstract （68）   HTML （0）    PDF （792KB）（18）       Knowledge map    The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of 85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constant-depth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit-Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic fields. Finally, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms. Select Generating attosecond pulses with controllable polarization from cyclic H32+ molecules by bichromatic circular fields Si-Qi Zhang(张思琪), Bing Zhang(张冰), Bo Yan(闫博), Xiang-Qian Jiang(姜向前), and Xiu-Dong Sun(孙秀冬) Chin. Phys. B, 2024, 33 (2): 023301.   DOI: 10.1088/1674-1056/ad062b Abstract （62）   HTML （0）    PDF （1070KB）（68）       Knowledge map    We investigate the polarization properties of harmonics from the cyclic H32+ molecular ions in tailored bichromatic counter-rotating circularly polarized (BCCP) fields by solving the time-dependent Schrödinger equation. The allowed harmonics and their helicities are associated with the symmetry compatibility of the field-target systems, and large intensity difference between adjacent harmonics with opposite helicities appears in a wide spectral range when the BCCP field is at certain rotation angles. We try to explain the intensity difference by using a recombination model based on the quantum-orbit theory and by analyzing the ionization pathways. Moreover, to synthesize attosecond pulse trains with tunable polarization, the intensity difference is manipulated by introducing a seed XUV field, and by changing the relative amplitude ratio as well as the helicity of BCCP fields. Select Efficient loading of cesium atoms in a magnetic levitated dimple trap Guoqing Zhang(张国庆), Guosheng Feng(冯国胜), Yuqing Li(李玉清), Jizhou Wu(武寄洲), and Jie Ma(马杰) Chin. Phys. B, 2024, 33 (2): 023702.   DOI: 10.1088/1674-1056/ad0b03 Abstract （52）   HTML （0）    PDF （945KB）（14）       Knowledge map    We report a detailed study of magnetically levitated loading of ultracold 133Cs atoms in a dimple trap. The atomic sample was produced in a combined red-detuned optical dipole trap and dimple trap formed by two small waist beams crossing a horizontal plane. The magnetic levitation for the 133Cs atoms forms an effective potential for a large number of atoms in a high spatial density. Dependence of the number of atoms loaded and trapped in the dimple trap on the magnetic field gradient and bias field is in good agreement with the theoretical analysis. This method has been widely used to obtain the Bose-Einstein condensation atoms for many atomic species. Select Theoretical investigation of electron-impact ionization of W8+ ion Shiping Zhang(张世平), Fangjun Zhang(张芳军), Denghong Zhang(张登红), Xiaobin Ding(丁晓彬), Jun Jiang(蒋军), Luyou Xie(颉录有), Yulong Ma(马玉龙), Maijuan Li(李麦娟), Marek Sikorski, and Chenzhong Dong(董晨钟) Chin. Phys. B, 2024, 33 (3): 033401.   DOI: 10.1088/1674-1056/ad1487 Abstract （47）   HTML （0）    PDF （822KB）（64）       Knowledge map    The electron-impact single ionization cross section for W8+ ion has been calculated using flexible atomic code, employing the level-to-level distorted-wave approximation. This calculations takes into account contributions form both direct ionization (DI) and excitation autoionization (EA). However, the theoretical predictions, based solely on the ground state, tends to underestimate the experimental values. This discrepancy can be mitigated by incorporation contributions from excited states. We extended the theoretical analysis, including the contributions from the long-lived metastable states with lifetimes exceeding 1.5×10-5 s. We employed two statistical models to predict the fraction of ground state ions in the parent ion beam. Assuming a 79% fraction of parent ions in ground configuration, the experiment measurements align with the predictions. Furthermore we derived the theoretical cross-section for the ground state as correlated plasma rate coefficients, and compared it with existing data. Despite the uncertainty in our calculations, our results are still acceptable. Select Microscopic mechanism of plasmon-mediated photocatalytic H2 splitting on Ag-Au alloy chain Yuhui Song(宋玉慧), Yirui Lu(芦一瑞), Axin Guo(郭阿鑫), Yifei Cao(曹逸飞), Jinping Li(李金萍), Zhengkun Fu(付正坤), Lei Yan(严蕾), and Zhenglong Zhang(张正龙) Chin. Phys. B, 2024, 33 (3): 033101.   DOI: 10.1088/1674-1056/ad123d Abstract （45）   HTML （0）    PDF （3141KB）（53）       Knowledge map    Alloy nanostructures supporting localized surface plasmon resonances has been widely used as efficient photocatalysts, but the microscopic mechanism of alloy compositions enhancing the catalytic efficiency is still unclear. By using time-dependent density functional theory (TDDFT), we analyze the real-time reaction processes of plasmon-mediated H2 splitting on linear Ag-Au alloy chains when exposed to femtosecond laser pulses. It is found that H2 splitting rate depends on the position and proportion of Au atoms in alloy chains, which indicates that specially designed Ag-Au alloy is more likely to induce the reaction than pure Ag chain. Especially, more electrons directly transfer from the alloy chain to the anti-bonding state of H2, thereby accelerating the H2 splitting reaction. These results establish a theoretical foundation for comprehending the microscopic mechanism of plasmon-induced chemical reaction on the alloy nanostructures. Select Theoretical investigations of population trapping phenomena in atomic four-color, three-step photoionization scheme Xiao-Yong Lu(卢肖勇) and Ya-Peng Sun(孙亚鹏) Chin. Phys. B, 2024, 33 (3): 033202.   DOI: 10.1088/1674-1056/ad10fc Abstract （43）   HTML （1）    PDF （2660KB）（50）       Knowledge map    The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology. The population trapping phenomena and their influences are studied theoretically in monochromatic and non-monochromatic laser fields based on the density matrix theory in this work. Time evolutions of the photoionization properties of the four-color, three-step process are given. The population trapping effects occur intensely in monochromatic excitation, while it gradually turns weak as the laser bandwidth increases. The effects of bandwidth, Rabi frequency, time delay, and frequency detuning on the population trapping effect are investigated in monochromatic and non-monochromatic laser fields. The effects of laser process parameters and atomic parameters on the effective selective photoionization are also discussed. The ionization probability and selectivity factors, as evaluation indexes, are difficult to improve synchronously by adjusting systematic parameters. Besides, the existence of metastable state may play a negative role when its population is low enough. page Page 1 of 2 Total 25 records First page Prev page Next page Last page