State-selective charge exchange cross sections in collisions of highly-charged sulfur ions with helium and molecular hydrogen

The state-selective cross section data are useful for understanding and modeling the x-ray emission in celestial observations.In the present work,using the cold target recoil ion momentum spectroscopy,for the first time we investigated the state-selective single electron capture processes for S^(q+)–He and H_(2)(q=11–15)collision systems at an impact energy of q×20 keV and obtained the relative state-selective cross sections.The results indicate that only a few principal quantum states of the projectile energy level are populated in a single electron capture process.In particular,the increase of the projectile charge state leads to the population of the states with higher principal quantum numbers.It is also shown that the experimental averaged n-shell populations are reproduced well by the over-barrier model.The database is openly available in Science Data Bank at 10.57760/sciencedb.j00113.00091.

Measurement and analysis of species distribution in laser-induced ablation plasma of an aluminum–magnesium alloy

We proposed a theoretical spatio-temporal imaging method,which was based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamics model.By using the intensity formula,the integral intensity of spectral lines could be calculated and the corresponding images of intensity distribution could be drawn.Through further image processing such as normalization,determination of minimum intensity,combination and color filtering,a relatively clear species distribution image in the plasma could be obtained.Using the above method,we simulated the plasma ablated from Al-Mg alloy by different laser energies under 1 atm argon,and obtained the theoretical spatio-temporal distributions of Mg I,Mg II,Al I,Al II and Ar I species,which are almost consistent with the experimental results by differential imaging.Compared with the experimental decay time constants,the consistency is higher at low laser energy,indicating that our theoretical model is more suitable for the plasma dominated by laser-supported combustion wave.

Characterization of a microsecond pulsed non-equilibrium atmospheric pressure Ar plasma using laser scattering and optical emission spectroscopy

A non-equilibrium atmospheric pressure argon(Ar)plasma excited by microsecond pulse is studied experimentally by laser scattering and optical emission spectroscopy(OES),and theoretically by collisional-radiative(CR)model.More specifically,the electron temperature and electron density of plasma are obtained directly by the laser Thomson scattering,the gas temperature is measured by laser Raman scattering,the optical emissions of excited Ar states of plasma are measured by OES.The laser scattering results show that the electron temperature is about 1 eV which is similar to that excited by 60 Hz AC power,but the gas temperature is as low as 300 K compared to about 700 K excited by 60 Hz AC power.It is shown that the microsecond pulsed power supply,rather than nanosecond ones,is short enough to reduce the gas temperature of atmospheric pressure plasma to near room temperature.The electron temperature and electron density are also obtained by CR model based on OES,and find that the intensities of the optical emission intensity lines of 727.41,811.73,841.08,842.83,852.44 and 912.86 nm of Ar can be used to characterize the behavior of electron density and electron temperature,it is very useful to quickly estimate the activity of the atmospheric pressure Ar plasma in many applications.

Measurement and analysis of the extreme ultraviolet emission band of laser-produced antimony plasmas

The temporal evolution of extreme ultraviolet(EUV)emission spectra of laser-produced antimony(Sb)plasmas has been measured in the 7-16 nm wavelength region using spatio?temporally resolved lase-produced plasma spectroscopy technique.The spectral profiles involve an intense quasi-continuous band with superimposed intense characteristic radiation and are different with the increase of delay time.The spectral structures were also analyzed according to Hartree-Fock calculations with configuration interaction effects and contributed from 4d^4/;4d-4p,and 4d-5f unresolved transition arrays of Sb7*-Sb131.A steady-state collisionalradiative model was used to estimate the electron temperature and density range of Sb plasmas.This work would enrich the spectral data of highly-charged ions and provided a possible selection for developing EUV light sources.

The n-resolved single-electron capture in slow O^(6+)-Ne collisions

A study of single-electron capture(SEC) in 18-240 keV O^(6+)-Ne collisions has been conducted employing a combination of experimental and theoretical methodologies.Utilizing a reaction microscope,state-selective SEC cross sections and projectile scattering angle distributions were obtained.The translational energy spectra for SEC reveal the prevailing capture into n=3 states of the projectile ion,with a minor contribution from n=4 states.Notably,as the projectile's energy increases,the relative contribution of SEC n=4 states increases while that of SEC n=3 states diminishes.Furthermore,we computed state-selective relative cross sections and angular differential cross sections employing the classical molecular Coulomb over-the-barrier model(MCBM) and the multichannel Landau-Zener(MCLZ) model.A discernible discrepancy between the state-selective cross sections from the two theoretical models is apparent for the considered impact energies.However,regarding the angular differential cross sections,an overall agreement was attained between the current experimental results and the theoretical results from the MCLZ model.

Research on batch multielement rapid quantitative analysis based on the standard curve-assisted calibration-free laserinduced breakdown spectroscopy method

This study proposes a batch rapid quantitative analysis method for multiple elements by combining the advantages of standard curve(SC)and calibration-free laser-induced breakdown spectroscopy(CF-LIBS)technology to achieve synchronous,rapid,and accurate measurement of elements in a large number of samples,namely,SC-assisted CF-LIBS.Al alloy standard samples,divided into calibration and test samples,were applied to validate the proposed method.SC was built based on the characteristic line of Pb and Cr in the calibration sample,and the contents of Pb and Cr in the test sample were calculated with relative errors of 6%and 4%,respectively.SC built using Cr with multiple characteristic lines yielded better calculation results.The relative contents of ten elements in the test sample were calculated using CF-LIBS.Subsequently,the SC-assisted CF-LIBS was executed,with the majority of the calculation relative errors falling within the range of 2%-5%.Finally,the Al and Na contents of the Al alloy were predicted.The results demonstrate that it effectively enables the rapid and accurate quantitative analysis of multiple elements after a single-element SC analysis of the tested samples.Furthermore,this quantitative analysis method was successfully applied to soil and Astragalus samples,realizing an accurate calculation of the contents of multiple elements.Thus,it is important to advance the LIBS quantitative analysis and its related applications.

Estimating the grain size of microgranular material using laser-induced breakdown spectroscopy combined with machine learning algorithms

Recent work has validated a new method for estimating the grain size of microgranular materials in the range of tens to hundreds of micrometers using laser-induced breakdown spectroscopy(LIBS).In this situation,a piecewise univariate model must be constructed to estimate grain size due to the complex dependence of the plasma formation environment on grain size.In the present work,we tentatively construct a unified calibration model suitable for LIBS-based estimation of those grain sizes.Specifically,two unified multivariate calibration models are constructed based on back-propagation neural network(BPNN)algorithms using feature selection strategies with and without considering prior information.By detailed analysis of the performances of the two multivariate models,it was found that a unified calibration model can be successfully constructed based on BPNN algorithms for estimating the grain size in the range of tens to hundreds of micrometers.It was also found that the model constructed with a priorguided feature selection strategy had better prediction performance.This study has practical significance in developing the technology for material analysis using LIBS,especially when the LIBS signal exhibits a complex dependence on the material parameter to be estimated.

Analysis of metallic elements dissolution in the Astragalus at different decocting time by using LIBS technique

Astragalus is an important traditional Chinese herb that has therapeutic potential in the treatment of diseases. In this study, the dissolution of metallic elements during the material decoction process was investigated using laser-induced breakdown spectroscopy(LIBS). The Ca, Mg, Al, and Fe in the drug residues, liquid, and vapor were selected for the study of the transfer of elements after different decocting times. It was found that the intensities of the spectral lines for these elements in the drug liquid increased with increasing decocting times.The contrast trend was observed in the residues and only calcium was detected in the vapor.Furthermore, the relative mass concentrations of Ca, Mg, Al, and Fe in the liquid were quantitatively determined by a combination of the standard addition method and calibrationfree-LIBS method by adding the standard concentration solution of Cu and Cd elements into the drug liquids, it can be found that the maximum error between Cd concentration calculated by internal CF-LIBS and the standard is within 10%. This provides a new method of achieving the on-line monitoring and analysis of metallic elements in the production of traditional Chinese medicines.

Improved sensitivity on detection of Cu and Cr in liquids using glow discharge technology assisted with LIBS

Laser-induced breakdown spectroscopy-assisted glow discharge(LIBS-GD)for analysis of elements in liquid was proposed,and it was applied to detect heavy metals in highly sensitive mixed solutions of Cu and Cr.During the experiments of GD and LIBS-GD,the experimental parameters have been optimized and the optimal voltage is 450 V,laser energy is 60 mJ,and the delay time is 4000 ns.Furthermore,the calibration curves of Cu and Cr under GD and LIBS-GD experiments have been established,and the limits of detection(LODs)of Cu and Cr were obtained with the method of GD and LIBS-GD,respectively.The LOD of Cu decreased from3.37(GD)to 0.16 mg l(LIBS-GD),and Cr decreased from 3.15 to 0.34 mg l.The results prove that the capability of elemental detection under LIBS-GD has improved compared with the GD method.Therefore,LIBS-GD is expected to be developed into a highly sensitive method for sewage detection.

Influence of heating effect in Thomson scattering diagnosis of laser-produced plasmas in air

A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained as a function of the time delay which ranged from 300-3200 ns.The heating effect produced by the 532 nm probe beam with different energies on the air plasma at different interaction times was further studied using a time-resolved optical emission spectroscopy technique.The influence of the probe beam on the electron density was found to be negligible,whereas its influence on electron temperature is evident.In addition,the heating effect of the probe beam on the plasma strongly depends on the energy of the probe beam,and gradually weakens with increasing time delay.Our results are helpful for further understanding the TS method and its application in plasma diagnostics.

Fast identification of mural pigments at Mogao Grottoes using a LIBS-based spectral matching algorithm

To quickly identify the mineral pigments in the Dunhuang murals,a spectral matching algorithm(SMA)based on four methods was combined with laser-induced breakdown spectroscopy(LIBS)for the first time.The optimal range of LIBS spectrum for mineral pigments was determined using the similarity value between two different types of samples of the same pigment.A mineral pigment LIBS database was established by comparing the spectral similarities of tablets and simulated samples,and this database was successfully used to identify unknown pigments on tablet,simulated,and real mural debris samples.The results show that the SMA method coupled with the LIBS technique has great potential for identifying mineral pigments.

Numerical simulation of laser-induced plasma in background gas considering multiple interaction processes

Laser-induced plasma is often produced in the presence of background gas,which causes some new physical processes.In this work,a two-dimensional axisymmetric radiation fluid dynamics model is used to numerically simulate the expansion process of plasma under different pressures and gases,in which the multiple interaction processes of diffusion,viscosity and heat conduction between the laser ablated target vapor and the background gas are further considered,and the spatio-temporal evolutions of plasma parameters(species number density,expansion velocity,size and electron temperature)as well as the emission spectra are obtained.The consistency between the actual and simulated spectra of aluminum plasma in 1 atm argon verifies the correctness of the model and the numerical simulation,thus providing a refinement analysis method for the basic research of plasma expansion in gases and the application of laser-induced breakdown spectroscopy.

Analysis of extreme ultraviolet spectra of laser-produced Cd plasmas

In order to provide detailed information about Cd structure and gain more insight regarding ionization degrees and types of transition,as well as the understanding of the temporal evolution behavior of laser produced Cd plasmas,extreme ultraviolet spectra of laser-produced cadmium(Cd)plasmas have been measured in the 8.4-12 nm region using spatiotemporally resolved laser-produced plasma spectroscopy technique.Spectral features were analyzed by the Hartree-Fock(HF)method with relativistic correlations(HFR)using the Cowan code.The results showed that the 4p-5s resonance transition arrays from Cd^9+to Cd^13+merged to form intense lines in this spectral region.A number of new spectral features from Cd^9+and Cd^10+ions are reported in this study.Based on the assumption of a normalized Boltzmann distribution among the excited states associated with a steady-state collisional-radiative model,the plasma parameters were obtained by comparing the experimental and simulated spectra.As a result,we succeeded in reproducing the synthetic spectra for different time delays,which yielded good agreement with the experiments.The temporal evolution behaviors of electron temperature and electron density of plasma were also analyzed.

Numerical simulation of nanosecond laser ablation and plasma characteristics considering a real gas equation of state

Based on the governing equations which include the heat conduction equation in the target and the fluid equations of the vapor plasma,a two-dimensional axisymmetric model for ns-laser ablation considering the Knudsen layer and plasma shielding effect is developed.The equations of state of the plasma are described by a real gas approximation,which divides the internal energy into the thermal energy of atoms,ions and electrons,ionization energy and the excitation energy of atoms and ions.The dynamic evolution of the silicon target and plasma during laser ablation is studied by using this model,and the distributions of the temperature,plasma density,Mach number related to the evaporation/condensation of the target surface,laser transmissivity as well as internal energy of the plasma are given.It is found that the evolution of the target surface during laser ablation can be divided into three stages:(1)the target surface temperature increases continuously;(2)the sonic and subsonic evaporation;and(3)the subsonic condensation.The result of the internal energy distribution indicates that the ionization and excitation energy plays an important role in the internal energy of the plasma during laser ablation.This model is suitable for the case that the temperature of the target surface is lower than the critical temperature.

Effect of dielectronic recombination on charge-state distribution in laser-produced plasma based on steady-state collisional-radiative models

Armed with four different steady-state collisional-radiative(CR) models,we investigated the effect of dielectronic recombination(DR) on the charge-state distribution in laser-produced silicon plasma. To assess this effect,we performed a series of temporally resolved spectra of highly charged Si ions in the extreme ultraviolet region.Ab initio calculations of the DR rate coefficients were done for Si^(6+)–Si^(4+) ions. We also analyzed the evolution of the collisional ionization, radiative recombination, three-body recombination, photo-ionization, and DR rate coefficients as a function of electron temperature. The electron temperature and electron density for different delay times were obtained by comparing the normalized experimental and simulated spectra. The ion fraction and average charge state from the four different CR models were also obtained. The results indicate that the DR process has a greater influence in the stage of plasma evolution that cannot be neglected in plasma diagnoses.

Extreme ultraviolet spectral characteristic analysis of highly charged ions in laserproduced Cu plasmas

This paper reports the results of spectral measurements and a theoretical analysis of the temporal and spatial evolution of laser-produced Cu plasma in vacuum in the range of 8–14 nm.The time dependence of the extreme ultraviolet band spectrum at different positions near the target surface was obtained and found to be dominated by three broad-band features.The 3p and 3d excitations of Cu5+–Cu9+ions were calculated using the Hartree–Fock theory with configuration interactions.The characteristics of the spectral line distribution for the 3p–nd and 3d–nf transition arrays were analyzed.Based on the steady-state collisional radiation model and the normalized Boltzmann distribution,the complex spectral structure in the band of 13–14 nm is accurately explained through consistency comparisons and benchmarking between the experimental and theoretical simulation spectra,demonstrating that the structure mainly stems from the overlapping contribution of the 3d–4f and 3p–3d transition arrays for the Cu5+–Cu9+ions.These results may help in studying the radiation characteristics of isoelectronic series highly-charged ions involving the 3d excitation process.