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Tunable spectral continuous shift of high-order harmonic generation in atoms by a plasmon-assisted shaping pulse

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Chinese Physics B 2024年第3期33卷 433-440页

作者：王源李玉龙乔月高娜郭福明陈洲赫兰海杨玉军赵曦王俊 Institute of Atomic and molecular Physics Jilin UniversityChangchun 130012China Jilin Provincial Key Laboratory of Applied Atomic and molecular spectroscopy Jilin UniversityChangchun 130012China Beijing Institute of Space Launch Technology Beijing 100076China School of Physics and Information Technology Shaanxi Normal UniversityXi'an 710062China

We delve into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping *** findings reveal an intriguing manipulation of the frequency peak position in the harmonic emission by adjusting the absolute phase parameter within the frequency domain of the shaping *** phenomenon holds potential significance for experimental setups necessitating precisely tuned single ***,we observe a modulated shift in the created harmonic photon energy,spanning an impressive range of 1.2 *** frequency peak shift is rooted in the asymmetry exhibited by the rising and falling edges of the laser pulse,directly influencing the position of the peak frequency *** study quantifies the dependence of this tuning range and the asymmetry of the laser pulse,offering valuable insights into the underlying mechanisms driving this ***,our investigation uncovers the emergence of semi-integer order harmonics as the phase parameter is *** attribute this discovery to the intricate interference between harmonics generated by the primary and secondary return *** observation introduces an innovative approach for generating semi-integer order harmonics,thus expanding our understanding of high-order harmonic ***,our work contributes to the broader comprehension of complex phenomena in laser-matter interactions and provides a foundation for harnessing these effects in various applications,particularly those involving precise spectral control and the generation of unique harmonic patterns.

关键词： high-order harmonic semi-integer-order spectra shift inhomogeneous field

Internal collision double ionization of molecules driven by co-rotating two-color circularly polarized laser pulses

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Chinese Physics B 2024年第1期33卷 355-361页

作者：李雪峰乔月吴丹蔚瑞贤陈基根王俊郭福明杨玉军 Institute of Atomic and molecular Physics Jilin UniversityChangchun 130012China Jilin Provincial Key Laboratory of Applied Atomic and molecular spectroscopy Changchun 130012China School of Science Jilin Institute of Chemical TechnologyJilin 132022China Zhejiang Provincial Key Laboratory for Cutting Tools Taizhou UniversityJiaojiang 318000China

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.

关键词： non-sequential double ionization internuclear distance internal-collision circularly polarized laser field

Theoretical study of slowing supersonic CH_3F molecular beams using electrostatic Stark decelerator

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Chinese Physics B 2009年第1期18卷 149-156页

作者：邓联忠符广彬印建平 State Key Laboratory of Precision spectroscopy Department of PhysicsEast China Normal University

We have calculated the Stark effect of CH3F molecules in external electrical fields, the rotational population of supersonic CH3F molecules in different quantum states, and analyse the motion of weak-field-seeking CH3F molecules in a st＇ate ｜J = 1, KM = -1） inside the electrical field of a Stark decelerator by using a simple analytical model. Threedimensional Monte Carlo simulation is performed to simulate the dynamical slowing process of molecules through the decelerator, and the results are compared with those obtained from the analytical model, including the phase stability, slowing efficiency as well as the translational temperature of the slowed molecular packet. Our study shows that with a modest dipole moment （-1.85 Debye） and a relatively slight molecular weight （-34.03）, CH3F molecules in a state ｜J= 1, KM = -1） are a good candidate for slowing with electrostatic field. With high voltages of ±10 kV applied on the decelerator, molecules of 370 m/s can be brought to a standstill within 200 slowing stages.

关键词： molecular beam stark effect stark decelerator

Facile Development of Iron-Platinum Nanoparticles to Harness Multifunctionality in Single Entity

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Acta Metallurgica Sinica(English Letters) 2016年第12期29卷 1098-1106页

作者： Madhulekha Gogoi Komanduri S. Varadarajan Anant Bahadur Patel Pritam Deb Department of Physics Tezpur University (Central University) Tezpur Assam 784028 India NMR Microimaging and spectroscopy Centre for Cellularand Molecular Biology Habsiguda Hyderabad 500007 India Department of Chemistry IIT GuwahatiNorth Guwahati Assam 781039 India

Engineered magnetic nanosystems exhibit attractive options for implementing unique diagnostic options and therapeutic solutions in biomedical applications. Here we report a facile, thermo-free and aqueous synthetic method to prepare ascorbic acid-stabilized iron-platinum nanoparticles. The effects of reducing agent, pH and sequence of precursor addition are investigated, and optimized reaction condition is identified to obtain a unique iron-platinum （Pt-FePt） nanosystems. The multifunctionality of the developed nanosystem has been realized by catalytic efficiency of platinum for therapeutic application and superparamagnetic property of FePt for magnetic resonance imaging contrast enhancement. Moreover, the multifunctional imaging and therapeutic activities have been achieved at physiological pH. The developed multifunctional nanoparticles are monodisperse with uniform morphology as well as stable in solution and non-toxic.

关键词： Multifunctional Superparamagnetic Magnetic resonance imaging (MRI) Therapeutic

Deceleration of a continuous-wave (CW) molecular beam with a single quasi-CW semi-Gaussian laser beam

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Chinese Physics B 2008年第10期17卷 3672-3677页

作者：尹亚玲夏勇印建平 State Key Laboratory of Precision spectroscopy Department of PhysicsEast China Normal University

We propose a promising scheme to decelerate a CW molecular beam by using a red-detuned quasi-cw semi-Gaussian laser beam （SGB）. We study the dynamical process of the deceleration for a CW deuterated ammonia （ND3） molecular beam by Monte-Carlo simulation method. Our study shows that we can obtain a ND3 molecular beam with a relative average kinetic energy loss of about 10% and a relative output molecular number of more than 90% by using a single quasi-cw SGB with a power of 1.5kW and a maximum optical well depth of 7.33mK.

关键词： optical Stark deceleration semi-Gaussian beam

Reanalysis of the photoassociation spectrum of ^(133)Cs_2 (6P_(3/2)) 1_g state

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Chinese Physics B 2013年第8期22卷 375-379页

作者：马杰李玉清武寄洲樊群超冯灏孙卫国肖连团贾锁堂 State Key Laboratory of Quantum Optics and Quantum Optics Devices Laser Spectroscopy Laboratory Shanxi University School of Physics and Chemistry Research Center for Advanced Computation Xihua University Institute of Atomic and molecular Physics Sichuan University

Reanalysis of the photoassociation spectrum of the weakly binding （6S1/2 ＋ 6P3/2） lg 133Cs2 levels, reported in the previous study [J. Mol. Spectro. 255 （2009） 106], is performed by using a Lu-Fano graph coupled to the improved LeRoy- Bernstein formula including two additional modified terms. A more accurate coefficient （c3） is obtained for the leading long-range potential （-c3/R3） of a diatomic molecule.

关键词： photoassociation spectroscopy Lu-Fano graph improved LeRoy-Bernstein formula long-rangemolecular coefficient

MRCI+Q study of the low-lying electronic states of CdF including spin-orbit coupling

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Chinese Physics B 2017年第2期26卷 152-160页

作者： Shu-Tao Zhao Bing Yan Rui Li Shan Wu Qiu-Ling Wang School of Physics and Electronic Science Fuyang Normal University Fuyang 236037 China Jilin Provincial Key Laboratory of Applied Atomic and molecular spectroscopy （Jilin University） Institute of Atomic and molecular Physics Jilin University Changchun 130012 China Department of Physics College of Science Qiqihar University Qiqihar 161006 China

Cd F molecule, which plays an important role in a great variety of research fields, has long been subject to numerous researchers. Due to the unstable nature and heavy atom Cd containing in the Cd F molecule, electronic states of the molecule have not been well studied. In this paper, high accurate ab initio calculations on the Cd F molecule have been performed at the multi-reference configuration interaction level including Davidson correction（MRCI ＋ Q）. Adiabatic potential energy curves（PECs） of the 14 low-lying Λ–S states correlating with the two lowest dissociation limits Cd（~1S_g）＋ F（~2P_u） and Cd（~3P_u）＋ F（~2P_u） have been constructed. For the bound Λ–S and ？ states, the dominant electronic configurations and spectroscopic constants are obtained,and the calculated spectroscopic constants of bound states are consistent with previous experimental results. The dipole moments（DMs） of 2 Σ＋ and 2Π are determined, and the spin–orbit（SO） matrix elements between each pair of X2Σ＋, 22Σ＋, 12Π, and 22Π are obtained. The results indicate that the sudden changes of DMs and SO matrix elements arise from the variation of the electronic configurations around the avoided crossing region. Moreover,the Franck–Condon factors（FCFs）, the transition dipole moments（TDMs）, and radiative lifetimes of low-lying states-the ground state X2Σ＋are determined. Finally, the transitional properties of 22Π–X2Σ＋and 22Σ＋–X2Σ＋are studied. Based on our computed spectroscopic information of Cd F, the feasibility and challenge for laser cooling of Cd F molecule are discussed.

关键词： CdF spin–orbit coupling effect potential energy curves spectroscopic constant

All-Optical Production of Quantum Degeneracy and molecular Bose-Einstein Condensation of ~6Li

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Chinese Physics Letters 2015年第5期32卷 47-50页

作者：邓书金刁鹏鹏俞千里武海斌 State Key Laboratory of Precision spectroscopy Department of PhysicsEast China Normal University

We achieve a highly degenerate and strongly interacting Fermi gas in a mixture of the two lowest hyperfine states of 6 Li by direct evaporative cooling in a high power crossed optical dipole trap. The trap is loaded from a large atom number magneto-optical trap realized by a laser system of Z5-W intracavity-frequency-doubled light output at 671 nm. With this system, we also demonstrate the production of a molecular Bose-Einstein condensate （reBEC） of 6Li2, and observe the anisotropic expansion of Fermi gases in the so-called BEC-Bardeen-Cooper-Schrieffer crossover regime.

关键词： All-Optical Production of Quantum Degeneracy and molecular Bose-Einstein Condensation of BEC Li

Photoelectron imaging of resonance-enhanced multiphoton ionization and above-threshold ionization of ammonia molecules in a strong 800-nm laser pulse

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Chinese Physics B 2019年第6期28卷 140-145页

作者： Le-Le Song Ya-Nan Sun Yan-Hui Wang Xiao-Chun Wang Lan-Hai He Si-Zuo Luo Wen-Hui Hu Qiu-Nan Tong Da-Jun Ding Fu-Chun Liu Institute of Atomic and molecular Physics Jilin UniversityChangchun 130012China Jilin Institute of Chemical Technology Changchun 132022China Jilin Provincial Key Laboratory of Applied Atomic and molecular spectroscopy Jilin UniversityChangchun 130012China College of Electronic Science and Engineering State Key Laboratory on Integrated OptoelectronicsJilin UniversityChangchun 130012China

In this work, we mainly investigate the NH3 molecular multiphoton ionization process by using the photoelectron velocity map imaging technique. Under the condition of femtosecond laser(wavelength at 800 nm), the photoelectron images are detected. The channel switching and above-threshold ionization(ATI) effect are also confirmed. The kinetic energy spectrum(KES) and the photoelectron angular distributions(PADs) are obtained through the anti-Abel transformation from the original images, and then three ionization channels are confirmed successfully according to the Freeman resonance effect in a relatively low laser intensity region. In the excitation process, the intermediate resonance Rydberg states are C^1 A 1(6 + 2 photons process), B^1 E(6 + 2 photons process) and C^1 A 1(7 + 2 photons process), respectively. At the same time, we also find that the photoelectron angular distributions are independent of laser intensity. In addition, the electrons produced by different processes interfere with each other and they can produce a spider-like structure. We also find ac-Stark movement according to the Stark-shift-induced resonance effect when the laser intensity is relatively high.

关键词： photoelectron imaging Rydberg state resonance-enhanced multiphoton ionization photoelectron angular distribution