Low-density non–local-thermodynamic-equilibrium plasmas in intense radiation fields occur widely in inertial confinement fusion and astrophysics. Understanding the X-ray spectrum and the atomic kinetics of such plasm...Low-density non–local-thermodynamic-equilibrium plasmas in intense radiation fields occur widely in inertial confinement fusion and astrophysics. Understanding the X-ray spectrum and the atomic kinetics of such plasmas is therefore of great importance. However, the creation of uniform-density nonequilibrium plasmas in intense radiation fields in the laboratory and the measurement of their spectra with high resolution are challenging tasks. Here, we present a new method to produce such a uniform aluminum plasma and explore photon-induced kinetics and relevant atomic physics by measuring its spectrum. It is observed that in the presence of an external radiation field, the satellites q, r and a–d of the He-α resonance line are greatly enhanced compared with the satellites j, k, l. Analysis of atomic kinetics reveals that this effect of intense radiation is due to competition between the photoexcitation and autoionization processes. With this effect taken into account,simulated spectra are able to reproduce the measured spectra quite well.展开更多
Plasmas,the most common state of matter in the observable universe,are subject to instabilities of various types:hydrodynamic,magnetohydrodynamic,and electromagnetic.Our limited success in understanding these is due t...Plasmas,the most common state of matter in the observable universe,are subject to instabilities of various types:hydrodynamic,magnetohydrodynamic,and electromagnetic.Our limited success in understanding these is due to the lack of direct experimental information on their origins and evolution.Here,we present direct spatially resolved measurements of the femtosecond evolution of the electromagnetic beam-driven instability that arises from the interaction of forward and return currents in an ultrahigh-intensity laser-produced plasma.We track its evolution from the initial linear stage to the later nonlinear stage by measuring the spatiotemporal evolution of the giant(megagauss)magnetic field created in the interaction process.Our experimental findings and numerical simulations are the first to indicate the observed instability triggered by the emission of electromagnetic radiation,like those known in the context of gravitational interaction,where the emission of gravitational radiation drives specific negative-energy modes in rotating black holes or neutron stars.展开更多
Experiments with interacting high-velocity flows in a laser plasma can help answer fundamental questions in plasma physics and improve understanding of the mechanisms behind some astrophysical phenomena,such as the fo...Experiments with interacting high-velocity flows in a laser plasma can help answer fundamental questions in plasma physics and improve understanding of the mechanisms behind some astrophysical phenomena,such as the formation of collisionless shock waves,deceleration of accretion flows,and evolution of solar and stellar flares.This work presents the first direct experimental observations of stagnation and redirection of counterstreaming flows(jets)of laser plasma induced by intense laser pulses with intensity I~2×10^(18) W/cm^(2).Hybrid particlein-cell-fluid modeling,which takes into account the kinetic effects of ion motion and the evolution of the pressure tensor for electrons,demonstrates the compression of counterdirected toroidal self-generated magnetic fields embedded in counterstreaming plasma flows.The enhancement of the toroidal magnetic field in the interaction region results in plasma flow stagnation and redirection of the jets across the line of their initial propagation.展开更多
A singlet diatomic molecule naturally carries doubly degenerate ±Λ states when the projection of the total electronic angular momentum onto the internuclear axis is nonzero. These doubly degenerate states contri...A singlet diatomic molecule naturally carries doubly degenerate ±Λ states when the projection of the total electronic angular momentum onto the internuclear axis is nonzero. These doubly degenerate states contribute equally in conventional measurements and are thus treated the same in corresponding simulations. In this study, we demonstrate that in resonant excitation by intense laser pulses, the doubly degenerate ±Λ states must be clearly identified. This is exemplified in the X^(1)Σ → A^(1)Π transition of CO molecules. This distinction becomes especially important in the case of circularly polarized radiation. We attribute this phenomenon to the interference of electron-rotational pathways in the strong-field coupled transition with the ±Λ-state of the excited Π state. This research sheds light on the fundamental aspects of intense laser-molecule interactions when extending conventional theories.展开更多
Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-b...Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-based molecular ionization model and a laser field-assisted molecular dissociation model to elucidate experimental observations and predict potential applications.The predictions of these models have been corroborated by subsequent theoretical and experimental studies.This review highlights Professor Kong’s significant contributions to the study of molecular ionization and dissociation in intense femtosecond laser fields,emphasizing key advancements and outlining future directions in the field of strong-field laser chemistry.展开更多
A systematic investigation of the fifth-harmonic generation in H_(2)^(+),driven in the vicinity of a five-photon resonance by a linearly polarized laser field,has been carried out by numerically solving the full three...A systematic investigation of the fifth-harmonic generation in H_(2)^(+),driven in the vicinity of a five-photon resonance by a linearly polarized laser field,has been carried out by numerically solving the full three-dimensional time-dependent Schrödinger equation.We observe a pronounced enhancement of the fifth harmonic,while the intensities of the adjacent harmonics are significantly suppressed.Our analysis shows that such an enhancement of the fifth harmonic is mainly caused by the multiphoton resonance transition,as well as multichannel interference.In addition,we investigate the dependence of harmonic emission on laser intensity and molecular orientation to identify the optimal conditions for enhancing the fifth-harmonic generation.Our results provide useful insights for producing coherent ultraviolet radiation at 106 nm experimentally.展开更多
We propose an all-optical,single-laser-pulse scheme for generating a dense relativistic strongly magnetized electron-positron pair plasma.The scheme involves the interaction of an extremely intense(I■10^(24) W/cm^(2)...We propose an all-optical,single-laser-pulse scheme for generating a dense relativistic strongly magnetized electron-positron pair plasma.The scheme involves the interaction of an extremely intense(I■10^(24) W/cm^(2))circularly polarized laser pulse with a solid-density target containing a conical cavity.Through full-scale three-dimensional particle-in-cell simulations that account for quantum electrodynamic effects,it is shown that this interaction results in two significant outcomes:first,the generation of quasi-static magnetic fields reaching tens of gigagauss,and,second,the production of large quantities of electron-positron pairs(up to 10^(13))via the Breit-Wheeler process.The e^(-)e^(+)plasma becomes trapped in the magnetic field and remains confined in a small volume for hundreds of femtoseconds,far exceeding the laser timescale.The dependence of pair plasma parameters,as well as the efficiency of plasma production and confinement,is discussed in relation to the properties of the laser pulse and the target.Realizing this scheme experimentally would enable the investigation of physical processes relevant to extreme astrophysical environments.展开更多
In a recent paper published in Phys.Rev.Lett.133,152503(2024),H.Zhang,T.Li,and X.Wang predicted that modern intense lasers can induce highly nonlinear responses in the 229 Th nucleus for the first time,which is an ast...In a recent paper published in Phys.Rev.Lett.133,152503(2024),H.Zhang,T.Li,and X.Wang predicted that modern intense lasers can induce highly nonlinear responses in the 229 Th nucleus for the first time,which is an astonishing effect of light-nucleus interactions.This phenomenon is underpinned by two key factors:(1)the presence of a very low-lying nuclear excited state and(2)a nuclear hyperfine mixing effect that significantly enhances light-nucleus coupling.The resulting highly nonlinear responses facilitate efficient nuclear excitation and enable coherent light emission from the nucleus,resulting in high harmonic generation.229 Th presents a promising platform for advancements in both laser-nuclear physics and nuclear clock development.The pioneering work by Zhang et al.marks a new frontier in light-matter interactions.展开更多
Strong-field terahertz waves not only have high peak power but also possess strong electromagnetic field components.When electrons encounters strong-field terahertz waves,a series of novel changes are induced,which ha...Strong-field terahertz waves not only have high peak power but also possess strong electromagnetic field components.When electrons encounters strong-field terahertz waves,a series of novel changes are induced,which have attracted extensive attention.This review first introduces common optical sources for strong-field terahertz emission,such as photoconductive antennas,optical rectification crystals,and air plasmas.Subsequently,recent applications of strong-field terahertz technology in material state modulation are presented,mainly including strong-field terahertz wave-driven hot carrier motion,coherent phonon control,spintronics,electron acceleration,and biomedicine.展开更多
Superexcited states of NO molecule and their neutral dissociation processes have been studied both experimentally and theoretically. Neutral excited N^＊ and O^＊ atoms are detected by fluorescence spectroscopy for th...Superexcited states of NO molecule and their neutral dissociation processes have been studied both experimentally and theoretically. Neutral excited N^＊ and O^＊ atoms are detected by fluorescence spectroscopy for the NO molecule upon interaction with 800 nm intense laser radiation of duration 60 fs and intensity 0.2 PW/cm^2. Intense laser pulse causes neutral dissociation of superexcited NO molecule by way of multiphoton excitation, which is equivalent to single photon excitation in the extreme-ultraviolet region by synchrotron radiation. Potential energy curves （PECs） are also built using the calculated superexcited state of NO^＋. In light of the PECs, direct dissociation and pre-dissociation mechanisms are proposed respectively for the neutral dissociation leading to excited fragments N^＊ and O^＊.展开更多
To observe the clinical changes of meibomian gland dysfunctipn(MGD)and ocular Demodex infestation after intense pulsed light(IPL)treatment to further examine the mechanism of IPL treating patients with MGD and ocular ...To observe the clinical changes of meibomian gland dysfunctipn(MGD)and ocular Demodex infestation after intense pulsed light(IPL)treatment to further examine the mechanism of IPL treating patients with MGD and ocular Demodex infestation.The medical records of 25 patients(49 eyes)with MGD treated with IPL,were retrospectively examined to determine outcomes.Associated ocular-surface parameters(ocular surface disease index,OSD1;lipid layer thickness,LLT;noninvasive first breakup time,NIF-BUT;noninvasive average breakup time,NIAvg?BUT;tear film breakup area,TBUA;Schirmer I Test,SIT;corneal fluorescein staining,CFS),eyelid margin abnormalities,meibum quality and expressibility,MG morphological parameters(macrostructure and microstructure),and the number of Demodex infestation were examined before and after treatment.The MG microstructure and the Demodex infestation were examined via in vivo confocal microscopy(IVCM).The results showed that there were statistically significant differences in associated ocular-surface parameters(all P<0.05)before and after IPL treatment,except SIT(P=0.065).Eyelid margin abnormalities,meibum quality and expressibility obviously improved in upper and lower eyelid after IPL treatment(all P<0.0001).MG macrostructure(MG dropouts)decreased in upper(P=0.002)and lower eyelid(P=0.001)after IPL treatment.The nine parameters of MG microstructure in upper and lower eyelid all distinctly improved after IPL treatment(all P<0.0001).The mean number of Demodex mites on the upper lid margin(6.59±7.16 to 3.12±3.81/9 eyelashes)and lower lid margin(2.55±2.11 to 1.29±1.53/9 eyelashes)significantly reduced after IPL treatment(all P<0.0001).The Demodex eradication rate was 20%(8/40)in upper lid margin and 34.15%(14/41)in lower lid margin.These findings indicate that IPL shows great therapeutic potential for patients of MGD and ocular Demodex infestation.展开更多
AIM: To compare the anti-inflammatory effects of intense pulsed light(IPL) with tobramycin/dexamethasone plus warm compress through clinical signs and cytokines in tears.METHODS: Eighty-two patients with dry eye disea...AIM: To compare the anti-inflammatory effects of intense pulsed light(IPL) with tobramycin/dexamethasone plus warm compress through clinical signs and cytokines in tears.METHODS: Eighty-two patients with dry eye disease(DED) associated meibomian gland dysfunction(MGD) were divided into two groups. Group A was treated with IPL, and Group B was treated with tobramycin/dexamethasone plus warm compress. Ocular Surface Disease Index(OSDI), tear film breakup time(TBUT), corneal fluorescein staining(CFS), meibomian gland expressibility(MGE), meibum quality, gland dropout and tear cytokine levels were evaluated before treatment, 1 wk and 1 mo after treatment. RESULTS: TBUT in Group A was higher(P=0.035), and MGE score was lower than Group B at 1 mo(P=0.001). The changes of interleukin(IL)-17 A and IL-1β levels in tears were lower in Group A compared with that in Group B at 1 wk after treatment(P=0.05, P=0.005).CONCLUSION: Treatment with IPL can improve TBUT and MGE and downregulate levels of IL-17 A and IL-1β in tears of patients with DED associated MGD better than treatment with tobramycin/dexamethasone plus warm compress in one-month treatment period.展开更多
Using Joint Warning Typhoon Center （JTWC） best track data during the period 1948-2010, decadal and interdecadal changes of annual category 4 and 5 tropical cyclone （TC） frequency in the western North Pacific basin...Using Joint Warning Typhoon Center （JTWC） best track data during the period 1948-2010, decadal and interdecadal changes of annual category 4 and 5 tropical cyclone （TC） frequency in the western North Pacific basin were examined. By allowing all of the observed TCs in the JTWC dataset to move along the observed TC tracks in a TC intensity model, the annual category 4 and 5 TC frequency was simulated. The results agreed well with observations when the TC intensity prior to 1973 was adjusted based on time-dependent biases due to changes in measurement and reporting practices. The simulated and adjusted time series showed significant decadal （12-18 years） variability, while the interdecadal （18-32 years） variability was found to be statistically insignificant. Numerical simulations indicated that changes in TC tracks are the most important factor for the decadal variability in the category 4 and 5 TC frequency in the western North Pacific basin, while a combined effect of changes in SST and vertical wind shear also contributes to the decadal variability. Further analysis suggested that the active phase of category 4 and 5 TCs is closely associated with an eastward shift in the TC formation locations, which allows more TCs to follow a longer journey, favoring the development of category 4 and 5 TCs. The active phase corresponds with the SST warming over the tropical central and eastern Pacific and the eastward extension of the monsoon trough, thus leading to the eastward shift in TC formation locations.展开更多
Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution（MILD） combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation（EGR）,espe-cially C...Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution（MILD） combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation（EGR）,espe-cially CO2 in EGR gases,on ignition characteristics.Specifically,effects of CO2 addition on autoignition delay time were emphasized at temperature between 1200 K and 1600 K for a wide range of the lean-to-rich equivalence ratio（0.2~2）.The results showed that the ignition delay time increased with equivalence ratio or CO2 dilution ratio.Fur-thermore,ignition delay time was seen to be exponentially related with the reciprocal of initial temperature.Special concern was given to the chemical effects of CO2 on the ignition delay time.The enhancement of ignition delay time with CO2 addition can be mainly ascribed to the decrease of H,O and OH radicals.The predictions of tem-perature profiles and mole fractions of CO and CO2 were strongly related to the chemical effects of CO2.A single ignition time correlation was obtained in form of Arrhenius-type for the entire range of conditions as a function of temperature,CH4 mole fraction and O2 mole fraction.This correlation could successfully capture the complex be-haviors of ignition of CH4/air/CO2 mixture.The results can be applied to MILD combustion as ＂reference time＂,for example,to predict ignition delay time in turbulent reacting flow.展开更多
Employing the two-state model and the time-dependent wave packet method, we have investigated the influences of the parameters of the intense femtosecond laser field on the evolution of the wave packet, as well as the...Employing the two-state model and the time-dependent wave packet method, we have investigated the influences of the parameters of the intense femtosecond laser field on the evolution of the wave packet, as well as the population of ground and double-minimum electronic states of the NaRb molecule. For the different laser wavelengths, the evolution of the wave packet of 6{ }^1／Sigma ^ ＋ state with time and internuclear distance is different, and the different laser intensity brings different influences on the population of the electronic states of the NaRb molecule. One can control the evolutions of wave packet and the population in each state by varying the laser parameters appropriately, which will be a benefit for the light manipulation of atomic and molecular processes.展开更多
High-energy electron radiography(HEER)is a promising diagnostic tool for high-energy-density physics,as an alternative to tools such as X/γ-ray shadowgraphy and high-energy proton radiography.Impressive progress has ...High-energy electron radiography(HEER)is a promising diagnostic tool for high-energy-density physics,as an alternative to tools such as X/γ-ray shadowgraphy and high-energy proton radiography.Impressive progress has been made in the development and application ofHEER in the past fewyears,and its potential for high-resolution imaging of static opaque objects has been proved.In this study,by taking advantage of the short pulse duration and tunable time structure of high-energy electron probes,time-resolved imaging measurements of high-energy-density gold irradiated by ultrashort intense laser pulses are performed.Phenomena at different time scales frompicoseconds to microseconds are observed,thus proving the feasibility of this technique for imaging of static and dynamic objects.展开更多
A new moving or dynamic thermal tensioning technique-welding with trailing intense cooling was numerically simulated by finite element method(FEM)and experimentally investigated.The simulation results indicate that tr...A new moving or dynamic thermal tensioning technique-welding with trailing intense cooling was numerically simulated by finite element method(FEM)and experimentally investigated.The simulation results indicate that trailing intense cooling can increase significantly the longitudinal tensile plastic strain within the weld and its adjacent zone during cooling stage,which can partially or completely counterbalance the longitudinal compressive plastic strain formed in the heating stage and the solidification shrinkage formed in the cooling stage.Therefore the longitudinal shrinkage remaining in the weld and the adjacent zone is greatly reduced,which means that the residual stresses in the weldments are kept in a lower value and the residual distortion can be mitigated effectively.Meanwhile a series of parametric studies were conducted to demonstrate the influences of several key parameters such as cooling distance, cooling power and cooling width on the effectiveness of distortion control.Experimental results also verify the effectiveness of this distortion control technique and the reliability of the numerical simulation.展开更多
^(62,64)Cu are radioisotopes of medical interest that can be used for positron emission tomography(PET)imaging.Moreover,64Cu hasβ−decay characteristics that allowfor targeted radiotherapy of cancer.In the present wor...^(62,64)Cu are radioisotopes of medical interest that can be used for positron emission tomography(PET)imaging.Moreover,64Cu hasβ−decay characteristics that allowfor targeted radiotherapy of cancer.In the present work,a novel approach to experimentally demonstrate the production of ^(62,64)Cu isotopes fromphotonuclear reactions is proposed in which large-current laser-based electron(e−)beams are generated fromthe interaction between sub-petawatt laser pulses and near-critical-density plasmas.According to simulations,at a laser intensity of 3.431021 W/cm2,a dense e−beamwith a total charge of 100 nCcan be produced,and this in turn produces bremsstrahlung radiation of the order of 1010 photons per laser shot,in the region of the giant dipole resonance.The bremsstrahlung radiation is guided to a natural Cu target,triggering photonuclear reactions to produce themedical isotopes ^(62,64)Cu.An optimal target geometry is employed to maximize the photoneutron yield,and ^(62,64)Cuwith appropriate activities of 0.18 GBq and 0.06 GBq are obtained for irradiation times equal to their respective half-livesmultiplied by three.The detection of the characteristic energy for the nuclear transitions of ^(62,64)Cu is also studied.The results of our calculations support the prospect of producing PET isotopes with gigabecquerel-level activity(equivalent to the required patient dose)using upcoming high-intensity laser facilities.展开更多
High-energyγ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled,and a number of mechanisms are propo...High-energyγ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled,and a number of mechanisms are proposed.Owing to the small cross section,these processes require both an ultra-intense laser field and a relativistic electron bunch.The extreme conditions for such scenarios can be achieved through recent developments in laser technology.Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally.Highenergy positron beams generated via a multiphoton process have recently been observed too.This paper reviews the principles ofγ-ray emission and e+e−pair creation in the context of laser–plasma interaction.Several proposed experimental setups forγ-ray emission and e+e−pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of theγ-photon and positron beams produced for ultrashort(15 fs)and longer(150 fs)multi-petawatt laser beams.展开更多
The aim of this study was to evaluate the factors influencing the inactivation effect of intense pulsed light(IPL)on Aeromonas salmonicida grown on chicken meat and skin,and to further develop prediction models of ina...The aim of this study was to evaluate the factors influencing the inactivation effect of intense pulsed light(IPL)on Aeromonas salmonicida grown on chicken meat and skin,and to further develop prediction models of inactivation.In this work,chicken meat and skin inoculated with meat-borne A.salmonicida isolates were subjected to IPL treatments under different conditions.The results showed that IPL had obvious bactericidal effect in the chicken skin and thickness groups when the treatment voltage and time were 7 V combined with 5 s.In addition,the lethality curves of A.salmonicida were fitted under IPL conditions of 3.5-7.5 V.The comparison of statistical parameters revealed that the Weibull model could best fit the mortality curves and could accurately predict the mortality dynamic of A.salmonicida grown on chicken skin.And further a secondary model between the scale factor b and the treatment voltage in Weibull model was established using linear equations,which determined that the secondary model could accurately predict the inactivation of A.salmonicida.This study provides a theoretical basis for future prediction models of Aeromonas,and also provides new ideas for sterilization approaches of meat-borne Aeromonas.展开更多
基金supported by Science Challenge Project Nos.TZ2025013,TZ2018005,and TZ2018001the National Nature Science Foundation(NSFC)of China under Grant Nos.12335015,12375238,and 12374261National Safety Academic Fund(NSAF)Grant No.U2430206.
文摘Low-density non–local-thermodynamic-equilibrium plasmas in intense radiation fields occur widely in inertial confinement fusion and astrophysics. Understanding the X-ray spectrum and the atomic kinetics of such plasmas is therefore of great importance. However, the creation of uniform-density nonequilibrium plasmas in intense radiation fields in the laboratory and the measurement of their spectra with high resolution are challenging tasks. Here, we present a new method to produce such a uniform aluminum plasma and explore photon-induced kinetics and relevant atomic physics by measuring its spectrum. It is observed that in the presence of an external radiation field, the satellites q, r and a–d of the He-α resonance line are greatly enhanced compared with the satellites j, k, l. Analysis of atomic kinetics reveals that this effect of intense radiation is due to competition between the photoexcitation and autoionization processes. With this effect taken into account,simulated spectra are able to reproduce the measured spectra quite well.
基金Department of Atomic Energy(DAE)for long-term support of this research,at present from the grant“Physics and Astronomy(Project Identification No.RTI4002)Department of Atomic Energy,Tata Institute of Fundamental Research”and partially from Grant No.JBR/2020/00039 of the Anusandhan National Research Foundation(ANRF),both agencies of the Government of Indiasupport from the ANRF through the J.C.Bose Fellowship Grant No.JCB/2017/000055 and Core Research Grant(CRG)Proposal Nos.ANRF/JBG/2025/000237/PS and CRG/2022/002782+1 种基金partial support from the Infosys-TIFR Leading Edge Research Grant(Cycle 2)the OSIRIS Consortium,consisting of UCLA and IST(Lisbon,Portugal),for providing access to the OSIRIS framework,which is work supported by Grant No.NSF ACI-1339893.
文摘Plasmas,the most common state of matter in the observable universe,are subject to instabilities of various types:hydrodynamic,magnetohydrodynamic,and electromagnetic.Our limited success in understanding these is due to the lack of direct experimental information on their origins and evolution.Here,we present direct spatially resolved measurements of the femtosecond evolution of the electromagnetic beam-driven instability that arises from the interaction of forward and return currents in an ultrahigh-intensity laser-produced plasma.We track its evolution from the initial linear stage to the later nonlinear stage by measuring the spatiotemporal evolution of the giant(megagauss)magnetic field created in the interaction process.Our experimental findings and numerical simulations are the first to indicate the observed instability triggered by the emission of electromagnetic radiation,like those known in the context of gravitational interaction,where the emission of gravitational radiation drives specific negative-energy modes in rotating black holes or neutron stars.
基金supported by Russian Science Foundation Grant No.24-62-00032.
文摘Experiments with interacting high-velocity flows in a laser plasma can help answer fundamental questions in plasma physics and improve understanding of the mechanisms behind some astrophysical phenomena,such as the formation of collisionless shock waves,deceleration of accretion flows,and evolution of solar and stellar flares.This work presents the first direct experimental observations of stagnation and redirection of counterstreaming flows(jets)of laser plasma induced by intense laser pulses with intensity I~2×10^(18) W/cm^(2).Hybrid particlein-cell-fluid modeling,which takes into account the kinetic effects of ion motion and the evolution of the pressure tensor for electrons,demonstrates the compression of counterdirected toroidal self-generated magnetic fields embedded in counterstreaming plasma flows.The enhancement of the toroidal magnetic field in the interaction region results in plasma flow stagnation and redirection of the jets across the line of their initial propagation.
基金supported by the National Natural Science Foundation of China(Grant No.12374238)the Postdoctoral Science Foundation of Shaanxi Province (Grant No.2024BSHSDZZ148)Ministry of Science and Higher Education of Russian Federation (Grant No.FSRZ 2023-0006)。
文摘A singlet diatomic molecule naturally carries doubly degenerate ±Λ states when the projection of the total electronic angular momentum onto the internuclear axis is nonzero. These doubly degenerate states contribute equally in conventional measurements and are thus treated the same in corresponding simulations. In this study, we demonstrate that in resonant excitation by intense laser pulses, the doubly degenerate ±Λ states must be clearly identified. This is exemplified in the X^(1)Σ → A^(1)Π transition of CO molecules. This distinction becomes especially important in the case of circularly polarized radiation. We attribute this phenomenon to the interference of electron-rotational pathways in the strong-field coupled transition with the ±Λ-state of the excited Π state. This research sheds light on the fundamental aspects of intense laser-molecule interactions when extending conventional theories.
基金supported by the National Key R&D Program of China(No.2023YFA1406801)the National Natural Science Foundation of China(Nos.12174011,12434013).
文摘Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-based molecular ionization model and a laser field-assisted molecular dissociation model to elucidate experimental observations and predict potential applications.The predictions of these models have been corroborated by subsequent theoretical and experimental studies.This review highlights Professor Kong’s significant contributions to the study of molecular ionization and dissociation in intense femtosecond laser fields,emphasizing key advancements and outlining future directions in the field of strong-field laser chemistry.
基金supported by the National Natural Science Foundation of China(Grant No.12264039)the Natural Science Foundation of Ningxia(Grant No.2024AAC03013)。
文摘A systematic investigation of the fifth-harmonic generation in H_(2)^(+),driven in the vicinity of a five-photon resonance by a linearly polarized laser field,has been carried out by numerically solving the full three-dimensional time-dependent Schrödinger equation.We observe a pronounced enhancement of the fifth harmonic,while the intensities of the adjacent harmonics are significantly suppressed.Our analysis shows that such an enhancement of the fifth harmonic is mainly caused by the multiphoton resonance transition,as well as multichannel interference.In addition,we investigate the dependence of harmonic emission on laser intensity and molecular orientation to identify the optimal conditions for enhancing the fifth-harmonic generation.Our results provide useful insights for producing coherent ultraviolet radiation at 106 nm experimentally.
基金supported by BMBF-Project No.05P24PF1DFG Project No.PU 213/6-3.
文摘We propose an all-optical,single-laser-pulse scheme for generating a dense relativistic strongly magnetized electron-positron pair plasma.The scheme involves the interaction of an extremely intense(I■10^(24) W/cm^(2))circularly polarized laser pulse with a solid-density target containing a conical cavity.Through full-scale three-dimensional particle-in-cell simulations that account for quantum electrodynamic effects,it is shown that this interaction results in two significant outcomes:first,the generation of quasi-static magnetic fields reaching tens of gigagauss,and,second,the production of large quantities of electron-positron pairs(up to 10^(13))via the Breit-Wheeler process.The e^(-)e^(+)plasma becomes trapped in the magnetic field and remains confined in a small volume for hundreds of femtoseconds,far exceeding the laser timescale.The dependence of pair plasma parameters,as well as the efficiency of plasma production and confinement,is discussed in relation to the properties of the laser pulse and the target.Realizing this scheme experimentally would enable the investigation of physical processes relevant to extreme astrophysical environments.
文摘In a recent paper published in Phys.Rev.Lett.133,152503(2024),H.Zhang,T.Li,and X.Wang predicted that modern intense lasers can induce highly nonlinear responses in the 229 Th nucleus for the first time,which is an astonishing effect of light-nucleus interactions.This phenomenon is underpinned by two key factors:(1)the presence of a very low-lying nuclear excited state and(2)a nuclear hyperfine mixing effect that significantly enhances light-nucleus coupling.The resulting highly nonlinear responses facilitate efficient nuclear excitation and enable coherent light emission from the nucleus,resulting in high harmonic generation.229 Th presents a promising platform for advancements in both laser-nuclear physics and nuclear clock development.The pioneering work by Zhang et al.marks a new frontier in light-matter interactions.
基金supported by the National Natural Science Foundation of China(No.12204251)。
文摘Strong-field terahertz waves not only have high peak power but also possess strong electromagnetic field components.When electrons encounters strong-field terahertz waves,a series of novel changes are induced,which have attracted extensive attention.This review first introduces common optical sources for strong-field terahertz emission,such as photoconductive antennas,optical rectification crystals,and air plasmas.Subsequently,recent applications of strong-field terahertz technology in material state modulation are presented,mainly including strong-field terahertz wave-driven hot carrier motion,coherent phonon control,spintronics,electron acceleration,and biomedicine.
文摘Superexcited states of NO molecule and their neutral dissociation processes have been studied both experimentally and theoretically. Neutral excited N^＊ and O^＊ atoms are detected by fluorescence spectroscopy for the NO molecule upon interaction with 800 nm intense laser radiation of duration 60 fs and intensity 0.2 PW/cm^2. Intense laser pulse causes neutral dissociation of superexcited NO molecule by way of multiphoton excitation, which is equivalent to single photon excitation in the extreme-ultraviolet region by synchrotron radiation. Potential energy curves （PECs） are also built using the calculated superexcited state of NO^＋. In light of the PECs, direct dissociation and pre-dissociation mechanisms are proposed respectively for the neutral dissociation leading to excited fragments N^＊ and O^＊.
基金This study was supported by the National Natural Science Foundation of China(No.81670824)the Natural Science Foundation of Hubei Province of China(No.2016CFB421).
文摘To observe the clinical changes of meibomian gland dysfunctipn(MGD)and ocular Demodex infestation after intense pulsed light(IPL)treatment to further examine the mechanism of IPL treating patients with MGD and ocular Demodex infestation.The medical records of 25 patients(49 eyes)with MGD treated with IPL,were retrospectively examined to determine outcomes.Associated ocular-surface parameters(ocular surface disease index,OSD1;lipid layer thickness,LLT;noninvasive first breakup time,NIF-BUT;noninvasive average breakup time,NIAvg?BUT;tear film breakup area,TBUA;Schirmer I Test,SIT;corneal fluorescein staining,CFS),eyelid margin abnormalities,meibum quality and expressibility,MG morphological parameters(macrostructure and microstructure),and the number of Demodex infestation were examined before and after treatment.The MG microstructure and the Demodex infestation were examined via in vivo confocal microscopy(IVCM).The results showed that there were statistically significant differences in associated ocular-surface parameters(all P<0.05)before and after IPL treatment,except SIT(P=0.065).Eyelid margin abnormalities,meibum quality and expressibility obviously improved in upper and lower eyelid after IPL treatment(all P<0.0001).MG macrostructure(MG dropouts)decreased in upper(P=0.002)and lower eyelid(P=0.001)after IPL treatment.The nine parameters of MG microstructure in upper and lower eyelid all distinctly improved after IPL treatment(all P<0.0001).The mean number of Demodex mites on the upper lid margin(6.59±7.16 to 3.12±3.81/9 eyelashes)and lower lid margin(2.55±2.11 to 1.29±1.53/9 eyelashes)significantly reduced after IPL treatment(all P<0.0001).The Demodex eradication rate was 20%(8/40)in upper lid margin and 34.15%(14/41)in lower lid margin.These findings indicate that IPL shows great therapeutic potential for patients of MGD and ocular Demodex infestation.
基金Supported by National Natural Science Foundation of China (No. 81570813)the Lin Hu Scientific Research Foundation of Department of Ophthalmology, Peking University Third Hospital+1 种基金the Scientific Research Foundation for the Excellent Returned Overseas Chinese Scholars, Peking University Third Hospitalthe Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry
文摘AIM: To compare the anti-inflammatory effects of intense pulsed light(IPL) with tobramycin/dexamethasone plus warm compress through clinical signs and cytokines in tears.METHODS: Eighty-two patients with dry eye disease(DED) associated meibomian gland dysfunction(MGD) were divided into two groups. Group A was treated with IPL, and Group B was treated with tobramycin/dexamethasone plus warm compress. Ocular Surface Disease Index(OSDI), tear film breakup time(TBUT), corneal fluorescein staining(CFS), meibomian gland expressibility(MGE), meibum quality, gland dropout and tear cytokine levels were evaluated before treatment, 1 wk and 1 mo after treatment. RESULTS: TBUT in Group A was higher(P=0.035), and MGE score was lower than Group B at 1 mo(P=0.001). The changes of interleukin(IL)-17 A and IL-1β levels in tears were lower in Group A compared with that in Group B at 1 wk after treatment(P=0.05, P=0.005).CONCLUSION: Treatment with IPL can improve TBUT and MGE and downregulate levels of IL-17 A and IL-1β in tears of patients with DED associated MGD better than treatment with tobramycin/dexamethasone plus warm compress in one-month treatment period.
基金jointly supported by the National Natural Science Foundation of China(Grant No.41305050)the Natural Science Foundation of the Jiangsu Higher Education Institutions(Grant No.11KJB170009)+3 种基金the Typhoon Research Project(Grant No.2009CB421503)the Social Commonwealth Research Program of the Ministry of Science and Technology of the People’s Republic of China(Grant No.GYHY200806009)the Key Laboratory of Meteorological Disaster of the Ministry of Education Program(Grant No.KLME1204)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Using Joint Warning Typhoon Center （JTWC） best track data during the period 1948-2010, decadal and interdecadal changes of annual category 4 and 5 tropical cyclone （TC） frequency in the western North Pacific basin were examined. By allowing all of the observed TCs in the JTWC dataset to move along the observed TC tracks in a TC intensity model, the annual category 4 and 5 TC frequency was simulated. The results agreed well with observations when the TC intensity prior to 1973 was adjusted based on time-dependent biases due to changes in measurement and reporting practices. The simulated and adjusted time series showed significant decadal （12-18 years） variability, while the interdecadal （18-32 years） variability was found to be statistically insignificant. Numerical simulations indicated that changes in TC tracks are the most important factor for the decadal variability in the category 4 and 5 TC frequency in the western North Pacific basin, while a combined effect of changes in SST and vertical wind shear also contributes to the decadal variability. Further analysis suggested that the active phase of category 4 and 5 TCs is closely associated with an eastward shift in the TC formation locations, which allows more TCs to follow a longer journey, favoring the development of category 4 and 5 TCs. The active phase corresponds with the SST warming over the tropical central and eastern Pacific and the eastward extension of the monsoon trough, thus leading to the eastward shift in TC formation locations.
基金Supported by the National Natural Science Foundation of China (50206014)the Shuguang Scholar Program of Shanghai Education Development Foundation (05SG23)
文摘Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution（MILD） combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation（EGR）,espe-cially CO2 in EGR gases,on ignition characteristics.Specifically,effects of CO2 addition on autoignition delay time were emphasized at temperature between 1200 K and 1600 K for a wide range of the lean-to-rich equivalence ratio（0.2~2）.The results showed that the ignition delay time increased with equivalence ratio or CO2 dilution ratio.Fur-thermore,ignition delay time was seen to be exponentially related with the reciprocal of initial temperature.Special concern was given to the chemical effects of CO2 on the ignition delay time.The enhancement of ignition delay time with CO2 addition can be mainly ascribed to the decrease of H,O and OH radicals.The predictions of tem-perature profiles and mole fractions of CO and CO2 were strongly related to the chemical effects of CO2.A single ignition time correlation was obtained in form of Arrhenius-type for the entire range of conditions as a function of temperature,CH4 mole fraction and O2 mole fraction.This correlation could successfully capture the complex be-haviors of ignition of CH4/air/CO2 mixture.The results can be applied to MILD combustion as ＂reference time＂,for example,to predict ignition delay time in turbulent reacting flow.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10674114 and 10604045)
文摘Employing the two-state model and the time-dependent wave packet method, we have investigated the influences of the parameters of the intense femtosecond laser field on the evolution of the wave packet, as well as the population of ground and double-minimum electronic states of the NaRb molecule. For the different laser wavelengths, the evolution of the wave packet of 6{ }^1／Sigma ^ ＋ state with time and internuclear distance is different, and the different laser intensity brings different influences on the population of the electronic states of the NaRb molecule. One can control the evolutions of wave packet and the population in each state by varying the laser parameters appropriately, which will be a benefit for the light manipulation of atomic and molecular processes.
基金This work was supported by the National Natural Science Foundation of China(NSFC Grant Nos.11435015 and 11505251).
文摘High-energy electron radiography(HEER)is a promising diagnostic tool for high-energy-density physics,as an alternative to tools such as X/γ-ray shadowgraphy and high-energy proton radiography.Impressive progress has been made in the development and application ofHEER in the past fewyears,and its potential for high-resolution imaging of static opaque objects has been proved.In this study,by taking advantage of the short pulse duration and tunable time structure of high-energy electron probes,time-resolved imaging measurements of high-energy-density gold irradiated by ultrashort intense laser pulses are performed.Phenomena at different time scales frompicoseconds to microseconds are observed,thus proving the feasibility of this technique for imaging of static and dynamic objects.
文摘A new moving or dynamic thermal tensioning technique-welding with trailing intense cooling was numerically simulated by finite element method(FEM)and experimentally investigated.The simulation results indicate that trailing intense cooling can increase significantly the longitudinal tensile plastic strain within the weld and its adjacent zone during cooling stage,which can partially or completely counterbalance the longitudinal compressive plastic strain formed in the heating stage and the solidification shrinkage formed in the cooling stage.Therefore the longitudinal shrinkage remaining in the weld and the adjacent zone is greatly reduced,which means that the residual stresses in the weldments are kept in a lower value and the residual distortion can be mitigated effectively.Meanwhile a series of parametric studies were conducted to demonstrate the influences of several key parameters such as cooling distance, cooling power and cooling width on the effectiveness of distortion control.Experimental results also verify the effectiveness of this distortion control technique and the reliability of the numerical simulation.
基金This work is supported by the National Natural Science Foundation of China(Grant No.11675075)the Natural Science Foundation of Hunan Province,China(Grant No.2018JJ2315)W.L.appreciates support from the Youth Talent Project of Hunan Province,China(Grant No.2018RS3096).
文摘^(62,64)Cu are radioisotopes of medical interest that can be used for positron emission tomography(PET)imaging.Moreover,64Cu hasβ−decay characteristics that allowfor targeted radiotherapy of cancer.In the present work,a novel approach to experimentally demonstrate the production of ^(62,64)Cu isotopes fromphotonuclear reactions is proposed in which large-current laser-based electron(e−)beams are generated fromthe interaction between sub-petawatt laser pulses and near-critical-density plasmas.According to simulations,at a laser intensity of 3.431021 W/cm2,a dense e−beamwith a total charge of 100 nCcan be produced,and this in turn produces bremsstrahlung radiation of the order of 1010 photons per laser shot,in the region of the giant dipole resonance.The bremsstrahlung radiation is guided to a natural Cu target,triggering photonuclear reactions to produce themedical isotopes ^(62,64)Cu.An optimal target geometry is employed to maximize the photoneutron yield,and ^(62,64)Cuwith appropriate activities of 0.18 GBq and 0.06 GBq are obtained for irradiation times equal to their respective half-livesmultiplied by three.The detection of the characteristic energy for the nuclear transitions of ^(62,64)Cu is also studied.The results of our calculations support the prospect of producing PET isotopes with gigabecquerel-level activity(equivalent to the required patient dose)using upcoming high-intensity laser facilities.
基金This work was supported by the projects ELITAS(No.CZ.02.1.01/0.0/0.0/16_013/0001793)High Field Initiative(No.CZ.02.1.01/0.0/0.0/15_003/0000449)+1 种基金both from the European Regional Development Fund.It was also supported by the project ADONIS(Advanced Research Using High Intensity Laser Produced Photons and Particles),No.CZ.02.1.01/0.0/0.0/16_019/0000789from the European Regional Development Fund.The support of Czech Science Foundation Project No.18-09560S is acknowledged.Computational resources were provided by the MetaCentrum under the Program No.LM2010005,by the IT4Innovations Centre of Excellence under the Project Nos.CZ.1.05/1.1.00/02.0070 and LM2011033,and by the ECLIPSE cluster of ELI-Beamlines.The EPOCH code was developed as part of the UKEPSRC-funded Project No.EP/G054940/1.
文摘High-energyγ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled,and a number of mechanisms are proposed.Owing to the small cross section,these processes require both an ultra-intense laser field and a relativistic electron bunch.The extreme conditions for such scenarios can be achieved through recent developments in laser technology.Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally.Highenergy positron beams generated via a multiphoton process have recently been observed too.This paper reviews the principles ofγ-ray emission and e+e−pair creation in the context of laser–plasma interaction.Several proposed experimental setups forγ-ray emission and e+e−pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of theγ-photon and positron beams produced for ultrashort(15 fs)and longer(150 fs)multi-petawatt laser beams.
基金supported by projects funded by grants from the Natural Science Foundation of Jiangsu Province in China(BK20221515)the National Natural Science Foundation of China(32172266)the Changzhou Science and Technology Support Program(CE20222002)。
文摘The aim of this study was to evaluate the factors influencing the inactivation effect of intense pulsed light(IPL)on Aeromonas salmonicida grown on chicken meat and skin,and to further develop prediction models of inactivation.In this work,chicken meat and skin inoculated with meat-borne A.salmonicida isolates were subjected to IPL treatments under different conditions.The results showed that IPL had obvious bactericidal effect in the chicken skin and thickness groups when the treatment voltage and time were 7 V combined with 5 s.In addition,the lethality curves of A.salmonicida were fitted under IPL conditions of 3.5-7.5 V.The comparison of statistical parameters revealed that the Weibull model could best fit the mortality curves and could accurately predict the mortality dynamic of A.salmonicida grown on chicken skin.And further a secondary model between the scale factor b and the treatment voltage in Weibull model was established using linear equations,which determined that the secondary model could accurately predict the inactivation of A.salmonicida.This study provides a theoretical basis for future prediction models of Aeromonas,and also provides new ideas for sterilization approaches of meat-borne Aeromonas.
