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Exploring the vacuum ultraviolet photochemistry of astrochemically important triatomic molecules

National Science Review 2023年第8期10卷 243-259页

作者： Yao Chang Michael N.R. Ashfold Kaijun Yuan Xueming Yang State Key Laboratory of Molecular Reaction Dynamics and Dalian coherent light source Dalian Institute of Chemical Physics Chinese Academy of Sciences School of Chemistry University of Bristol University of Chinese Academy of Sciences Hefei National Laboratory Department of Chemistry College of Science Southern University of Science and Technology

The recently constructed vacuum ultraviolet(VUV) free electron laser(FEL) at the Dalian coherent light source(DCLS) is yielding a wealth of new and exquisitely detailed information about the photofragmentation dynamics of many small gas-phase molecules. This review focuses particular attention on five triatomic molecules—H2O, H2S, CO2, OCS and CS2. Each shows excitation wavelength-dependent dissociation dynamics, yielding photofragments that populate a range of electronic and(in the case of diatomic fragments) vibrational and rotational quantum states, which can be characterized by different translational spectroscopy methods. The photodissociation of an isolated molecule from a well-defined initial quantum state provides a lens through which one can investigate how and why chemical reactions occur, and provides numerous opportunities for fruitful, synergistic collaborations with high-level ab initio quantum chemists. The chosen molecules, their photofragments and the subsequent chemical reaction networks to which they can contribute are all crucial in planetary atmospheres and in interstellar and circumstellar environments. The aims of this review are 3-fold: to highlight new photochemical insights enabled by the VUV-FEL at the DCLS, notably the recently recognized central atom elimination process that is shown to contribute in all of these triatomic molecules; to highlight some of the potential implications of this rich photochemistry to our understanding of interstellar chemistry and molecular evolution within the universe; and to highlight other and future research directions in areas related to chemical reaction dynamics and astrochemistry that will be enabled by increased access to VUV-FEL sources.

关键词： vacuum ultraviolet photochemistry photodissociation free electron laser interstellar chemistry chemistry of planetary atmospheres

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Coherence phase spectrum analyzer for a randomly fluctuated fractional vortex beam

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Photonics Research 2024年第1期12卷 33-39页

作者： ZHUOYI WANG XINGYUAN LU JIANBO GAO XUECHUN ZHAO QIWEN ZHAN YANGJIAN CAI CHENGLIANG ZHAO School of Physical Science and Technology Soochow UniversitySuzhou 215006China School of Optical-Electrical and Computer Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shandong Provincial Engineering and Technical Center of light Manipulations&Shandong Provincial Key Laboratory of Optics and Photonic Device School of Physics and ElectronicsShandong Normal UniversityJinan 250358China Shandong Joint Research Center of light Manipulation Science and Photonics Integrated Chip of East China Normal University and Shandong Normal University East China Normal UniversityShanghai 200241China

Fractional vortex beams exhibit a higher degree of modulation dimensions than conventional vortices,thus inheriting superior anti-turbulent transmission properties through the incorporation of additional coherence ***,aliasing the mixed modes induced by coherence degradation makes the quantitative measurement of the topological charge in fractional vortex beams *** this study,a coherence phase spectrum was introduced,and experimental demonstrations to quantitatively determine the fractional topological charge of partially coherent fractional vortex beams were *** leveraging the four-dimensional measurement of a partially coherent light field,the source coherence function was inversely reconstructed,and fractional topological charges were determined with high precision by extracting the phase spectrum of the coherence ***–Gaussian,elliptical Gaussian,and plane-wave-fraction vortex beams with various degrees of coherence were used to demonstrate measurement *** proposed method is applicable to X-rays and electron *** has potential applications in optical encryption,high-capacity optical communication,and quantum entanglement.

关键词： function fractional vortex

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Layer resolved magnetization reversal study in SmCo_5 /Fe nanocomposite bilayers

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Chinese Physics B 2010年第3期19卷 528-532页

作者： F.Shahzad S.A.Siddiqi M.Y.Im A.Avallone P.Fischer Z.Hussain I.Siddiqi F.Hellman Centre for Solid State Physics University of the PunjabLahore-54590Pakistan Center for X-ray Optics Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA Advanced light source Berkeley LaboratoryUniversity of CaliforniaBerkeleyCA-94720USA Department of Physics University of CaliforniaBerkeleyCalifornia-94720USA

A hard/soft SmCo5/ Fe nanocomposite magnetic bilayer system is fabricated on x-ray transparent 100-200 nm thin SiaN4 films by magnetron sputtering. The microscopic magnetic domain pattern and its behaviours during magnetization reversal in the hard and the soft magnetic phases are studied separately by element specific magnetic soft x-ray microscopy at a spatial resolution of better than 25 Nm. We observe that the domain patterns for the soft and hard phases show coherent behaviours in varying magnetic fields. We derive local M（H） curves from the images of Fe and SmCo5 separately and find the switches for hard and soft phases to be the same.

关键词： multilayers x-ray microscopes magnetic properties of nanostructures

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Breaking Mirror Circularly Polarized Luminescence of Chiral Metal-Organic Frameworks by High-Pressure Stimulation

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CCS Chemistry 2023年第10期5卷 2215-2224页

作者： Laizhi Sui Zhi-Bin Jin Guangming Niu Jutao Jiang Qiao-Hong Li Li-Mei Chang Kaijun Yuan Zhi-Gang Gu Jian Zhang Xueming Yang State Key Laboratory of Molecular Reaction Dynamics and Dalian coherent light source Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 110623 State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002 University of Chinese Academy of Sciences Beijing 100049 Marine Engineering College Dalian Maritime UniversityDalian 116026 Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China Fuzhou350108 Department of Chemistry College of ScienceSouthern University of Science and TechnologyShenzhen 518055

Understanding high-pressure-stimulated circularly polarized luminescence(CPL)of enantiomers remains a challenging but significant task in fundamental research and optical ***,we combined in situ high-pressure photoluminescence with circularly polarized light to study how high pressure stimulated the CPL of crystalline *** lanthanide(Ln)-tartrate(Tar)metal-organic frameworks(MOFs;Ln=Eu,Tb)were synthesized to study their CPL from atmospheric pressure to 10 *** atmospheric pressure,D-and L-Eu(Tar)showed strong andmirror *** intensity changes,emission wavelength shifts,and signal inversions were induced by increasing *** that the D-Eu(Tar)enantiomer showed strong CPL with a maximal dissymmetric factor(g_(lum))of 0.69 under 3 GPa,which is much higher than that under atmospheric pressure and of other reported MOF-based CPL *** interestingly,D-and L-Ln(Tar)enantiomers display obvious asymmetric CPL signals with increasing pressure,demonstrating that high pressure can break the mirror CPL of the MOF *** findings provide a critical understanding on in situ high-pressure CPL of chiral materials and establish a new optical phenomenon where high pressure can break the mirror CPL of enantiomers.

关键词： chirality metal-organic frameworks high pressure circularly polarized luminescence symmetry breaking

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Extreme ultraviolet radiation for coherent diffractive imaging with high spatial resolution

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Science China(Physics,Mechanics & Astronomy) 2010年第6期53卷 1065-1067页

作者： L.V. DAO S. TEICHMANN B. CHEN R.A. DILANIAN K.B. DINH P. HANNAFORD Centre for Atom Optics and Ultrafast Spectroscopy Swinburne University of Technology Australian Research Council Centre of Excellence for coherent X-Ray Science School of Physics University of Melbourne

Using different noble gases,argon,neon and helium,we are able to generate by high-harmonic generation(HHG) just a few harmonic orders in the spectral range 10-35 nm with a photon flux of～2.10 12 photons/(harmonic cm2 s) for argon and～10 10 photons/(harmonic cm2 s) for helium. The few-harmonic-order radiation is used for coherent diffractive imaging directly without any spectral filter. A spatial resolution of～100 nm is achieved using a～30 nm HHG source.

关键词： laser applications high harmonic generation coherent diffractive imaging

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Design and study of a high-current 5-cell superconducting rf cavity

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Chinese Physics C 2010年第5期34卷 603-605页

作者：刘振超 A. Nassiri G. Waldschmidt School of Physics Peking University Advanced Photon source Argonne National Laboratory9700 S Cass Ave.ArgonneIL 60439 USA

The Advanced Photon source （APS） at Argonne National Laboratory is considering the development of a superconducting linac-based fourth-generation hard X-ray source to meet future scientific needs of the hard X-ray user community. This work specifically focuses on the design of an optimized 5-cell superconducting radio-frequency structure well suited for a high-energy, high-beam-current energy recovery linac. The cavity design parameters are based on the APS storage ring nominal 7 GeV and 100 mA beam operation. A high-current 5-cell cw superconducting cavity operating at 1.4 GHz has been designed. In order to achieve a high current, the accelerating cavity shape has been optimized and large end-cell beam pipes have been adopted. The beam break-up threshold of the cavity has been estimated using the code TDBBU, which predicts a high threshold beam current for a 7 GeV energy recovery linac model. A copper prototype cavity has been fabricated that uses half-cell modules, initially assembled by clamping the cells together.

关键词： high current superconducting cavity higher order modes

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Realizing Attosecond Core-Level X-ray Spectroscopy for the Investigation of Condensed Matter Systems

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Ultrafast Science 2023年第4期3卷 1-13页

作者： Adam M.Summers Stefano Severino Maurizio Reduzzi Themistoklis P.H.Sidiropoulos Daniel E.Rivas Nicola Di Palo Hung-Wei Sun Ying-Hao Chien Iker Leon Barbara Buades Seth L.Cousin Stephan M.Teichmann Tobias Mey Klaus Mann Barbara Keitel Elke Plonjes Dmitri K.Efetov Heinrich Schwoerere Jens Biegert ICFO-Institut de Ciencies Fotoniques The Barcelona Institute of Science and Technology08860 CastelldefelsBarcelonaSpain linac coherent light source SLAC National Accelerator LaboratoryMenlo ParkCA 94025USA European XFEL Holzkoppel 422869 SchenefeldGermany Institut für Nanophotonik Göttingen e.V. Hans-Adolf-Krebs-Weg 137077 GöttingenGermany Deutsches Elektronen-Synchrotron Notkestraße 8522607 HamburgGermany Max-Planck-Institut für Struktur und Dynamik der Materie 22761 HamburgGermany ICREA Pg.Lluís Companys 2308010 BarcelonaSpain

Unraveling the exact nature of nonequilibrium and correlated interactions is paramount for continued progress in many areas of condensed matter science. Such insight is a prerequisite to develop an engineered approach for smart materials with targeted properties designed to address standing needs such as efficient light harvesting, energy storage, or information processing. For this goal, it is critical to unravel the dynamics of the energy conversion processes between carriers in the earliest time scales of the excitation dynamics. We discuss the implementation and benefits of attosecond soft x-ray core-level spectroscopy up to photon energies of 600 eV for measurements in solid-state systems. In particular, we examine how the pairing between coherent spectral coverage and temporal resolution provides a powerful new insight into the quantum dynamic interactions that determine the macroscopic electronic and optical response. We highlight the different building blocks of the methodology and point out the important aspects for its application from condensed matter studies to materials as thin as 25 nm. Furthermore, we discuss the technological developments in the field of tabletop attosecond soft x-ray sources with time-resolved measurements at the near and extended edge simultaneously and investigate the exciting prospective of extending such technique to the study of 2-dimensional materials.

关键词： Attosecond Science Core-level x-ray Spectroscopy High Harmonic Generation X-ray Absorption Ultrafast solid-state dynamics

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Design and performance of the LLRF control system for CSNS linac

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Radiation Detection Technology and Methods 2020年第2期4卷 196-202页

作者： Linyan Rong Zhencheng Mu Jian Li Zhexin Xie Wenzhong Zhou Bo Wang Maliang Wan Meifei Liu Xinan Xu Institute of High Energy Physics Chinese Academy of SciencesBeijingChina Spallation Neutron source Science Center DongguanChina

Objective The China Spallation Neutron source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first *** consists of RFQ,two bunchers of medium-energy beam transmission line,four DTL tanks and one debuncher of linac-to-ring beam transmission ***,eight online RF power sources are used to power these *** order to stabilize the amplitude,phase and resonant frequency of the RF accelerating field,and minimize beam loss,we have established digital low-level RF(LLRF)control *** The LLRF system includes RF reference line,analog module(AM),clock distribution module,digital control module(DCM),high-power protection module,timing and RF interlock module and so *** DCM is mainly responsible for the stability of the RF field amplitude and phase,and RF interlock module can quickly cut off the RF drive in case of arc in the RF transmission system,VSWR over threshold or cavity vacuum fault and so *** During beam commissioning,all of eight online units of LLRF control system were operating stably and *** amplitude and phase variations of the linac fields have been achieved about±0.4%and±0.15°with 10-mA beam loading,much better than the design requirements of±1%in amplitude and±1°in *** With the help of this system,we achieved stable operation under different beam ***,many important progresses have been achieved in the LLRF control system for amore convenient operation and a higher stability *** article describes the design and implementation of the LLRF for CSNS linac.

关键词： RF power source LLRF Reference system High-power protection Tracking resonant frequency of cavity

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Longitudinal beam dynamic design of 500 kW beam power upgrade for CSNS-II RCS

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Radiation Detection Technology and Methods 2022年第3期6卷 339-348页

作者： Hanyang Liu Sheng Wang Institute of High Energy Physics BeijingChina Spallation Neutron source Science Center Dongguan 523803China University of Chinese Academy of Sciences BeijingChina

Purpose The accelerator of the China Spallation Neutron source(CSNS)consists of an 80 MeV H-linac and a 1.6 GeV rapid cycling synchrotron(RCS).The design beam power is 100 kW,which has been *** the upgrade project(CSNS-II),the beam power will be upgraded to 500 kW by increasing the linac energy to 300 MeV and adding a dual harmonic RF system in the *** order to alleviate space charge effect and improve beam quality,the longitudinal beam dynamic of CSNS-II RCS dual harmonic RF system has been *** According to the longitudinal beam dynamic characteristics of CSNS-II RCS at different acceleration stages,the longitudinal emittance,bunching factor,momentumﬁlling factor and bunch length are studied and optimized in this *** and conclusions The optimized bunching factor is greatly improved,and the tune spread caused by space charge effect is greatly reduced in *** the suppressed space charge effects,the beam loss can be well controlled in CSNS-II RCS.

关键词： CSNS-II Space charge effect Dual-harmonic RF systems Longitudinal beam dynamics RCS

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AutoPhaseNN:unsupervised physics-aware deep learning of 3D nanoscale Bragg coherent diffraction imaging

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npj Computational Materials 2022年第1期8卷 1146-1153页

作者： Yudong Yao Henry Chan Subramanian Sankaranarayanan Prasanna Balaprakash Ross J.Harder Mathew J.Cherukara Advanced Photon source Argonne National LaboratoryLemontIL60439USA Center for Nanoscale Materials Argonne National LaboratoryLemontIL60439USA Mathematics and Computer Science Argonne National LaboratoryLemontIL60439USA

The problem of phase retrieval underlies various imaging methods from astronomy to nanoscale *** phase retrieval methods are iterative and are therefore computationally *** learning(DL)models have been developed to either provide learned priors or completely replace phase ***,such models require vast amounts of labeled data,which can only be obtained through simulation or performing computationally prohibitive phase retrieval on experimental *** 3D X-ray Bragg coherent diffraction imaging(BCDI)as a representative technique,we demonstrate AutoPhaseNN,a DL-based approach which learns to solve the phase problem without labeled *** incorporating the imaging physics into the DL model during training,AutoPhaseNN learns to invert 3D BCDI data in a single shot without ever being shown real space *** trained,AutoPhaseNN can be effectively used in the 3D BCDI data inversion about 100×faster than iterative phase retrieval methods while providing comparable image quality.

关键词： coherent iterative replace

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