Formic and acetic acids are the most abundant gaseous organic acids and play the key role in the atmospheric chemistry.In iodine-adduct chemical ionizationmass spectrometry(CIMS),the low utilization efficiency of meth...Formic and acetic acids are the most abundant gaseous organic acids and play the key role in the atmospheric chemistry.In iodine-adduct chemical ionizationmass spectrometry(CIMS),the low utilization efficiency of methyl iodide and humidity interference are two major issues of the vacuum ultraviolet(VUV)lamp initiated CIMS for on-line gaseous formic and acetic acids analysis.In this work,we present a new CIMS based on VUV lamp,and the ion-molecular reactor is separated into photoionization and chemical ionization zones by a reducer electrode.Acetone was added to the photoionization zone,and the VUV photoionization acetone provided low-energy electrons for methyl iodide to generate I−,and the addition of acetone reduced the amount of methyl iodide by 2/3.In the chemical ionization zone,a headspace vial containing ultrapure water was added for humidity calibration,and the vial changes the sensitivity as a function of humidity from ambiguity to well linear correlation(R2>0.95).With humidity calibration,the CIMS can quantitatively measure formic and acetic acids in the humidity range of 0%-88%RH.In this mode,limits of detection of 10 and 50 pptv are obtained for formic and acetic acids,respectively.And the relative standard deviation(RSD)of quantitation stability for 6 days were less than 10.5%.This CIMS was successfully used to determine the formic and acetic acids in the underground parking and ambient environment of the Shandong University campus(Qingdao,China).In addition,we developed a simple model based formic acid concentration to assess vehicular emissions.展开更多
Strong feld-induced nonsequential double ionization(NSDI)is a signifcant multi-electron phenomenon that provides crucial insights into understanding electron correlation and multiple ionization of atoms and molecules,...Strong feld-induced nonsequential double ionization(NSDI)is a signifcant multi-electron phenomenon that provides crucial insights into understanding electron correlation and multiple ionization of atoms and molecules,but it is typically unattainable in a circularly polarized laser pulse,especially for long-wavelength lasers.We present evidence that NSDI can occur in the presence of a near-infrared or beyond laser pulse by introducing a bowtie-nanotip.The laser-induced local plasmon can alter the local ellipticity of the feld,thereby enabling NSDI through elliptical trajectories that facilitate recollisions with parent atoms.An oval-shaped momentum distribution of recoiled ions provides evidence for the modifcation of trajectories by the aligned nanotips.Our study introduces an innovative control knob to manipulate NSDI and electron dynamics through the utilization of nanostructures.展开更多
We have conducted a two-color visible-ultraviolet （VIS-UV） resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron （PFI-PE） study of gaseous vana- dium mononitride （VN） in the total ...We have conducted a two-color visible-ultraviolet （VIS-UV） resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron （PFI-PE） study of gaseous vana- dium mononitride （VN） in the total energy range of 56900-59020 cm-1. The VN molecules were selectively excited to single rotational levels of the intermediate VN（D3H0, v＇=0） state by using a VIS dye laser prior to photoionization by employing a UV laser. This two-color scheme allows the measurements of rovibronically selected and re- solved PFI-PE spectra for the VN＋（X2A; v＋=0, 1, and 2） ion vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J＋=3/2 is determined to be the lowest rotational level of the ground electronic state, indicating that the symmetry of the ground VN＋ electronic state is 2A3/2. The analysis of the PFI-PE spectra for VN＋ also yields accurate values for the adiabatic ionization energy for the formation of VN＋（X2A3/2）, IE（VN）=56909.5＋0.8 cm-1 （7.05588±0.00010 eV）, the vibrational fre- quency wc＋=1068.0±0.8 cm-1, the anharmonicity constant wc＋Xe＋=5.8±0.8 cm-1, the rotational constants Be＋=0.6563±0.0005 cm-1 and ae＋=0.0069±0.0004 cm-1, and the equi-librium bond length, re＋=1.529A, for VN＋（X2A3/2）; along with the rotational constants Bc＋=0.6578i0.0028 cm-1 and a＋=0.0085±0.0028 cm-1, and the equilibrium bond length re＋=1.527A for VN＋（X2As/2）, and the spin-orbit coupling constant A=153.3±0.8 cm-1 for VN＋（X2/k5/2,3/2）. The highly precise energetic and spectroscopic data obtained in the present study are valuable for benchmarking the predictions based on state-of-the-art ab initio quantum calculations.展开更多
Traditional electrospray ionization tandem mass spectrometry(ESI-MS^(n))has been a powerful tool in diverse research areas,however,it faces great limitations in the study of protein-small molecule interactions.In this...Traditional electrospray ionization tandem mass spectrometry(ESI-MS^(n))has been a powerful tool in diverse research areas,however,it faces great limitations in the study of protein-small molecule interactions.In this article,the state-of-the-art temperature-controlled electrospray ionization tandem mass spectrometry(TC-ESI-MS^(n))is applied to investigate interactions between ubiquitin and two flavonol molecules,respectively.The combination of collision-induced dissociation(CID)and MS solution-melting experiments facilitates the understanding of flavonol-protein interactions in a new dimension across varying temperature ranges.While structural changes of proteins disturbed by small molecules are unseen in ESI-MS^(n),TC-ESI-MS^(n)allows a simultaneous assessment of the stability of the complex in both gas and liquid phases under various temperature conditions,meanwhile investigating the impact on the protein’s structure and tracking changes in thermodynamic data,and the characteristics of structural intermediates.展开更多
Accurate determination of lung cancer margins at the molecular level is of great significance to determine the optimal extent of resection during surgical operation and reduce the risk of postoperative recurrence.In t...Accurate determination of lung cancer margins at the molecular level is of great significance to determine the optimal extent of resection during surgical operation and reduce the risk of postoperative recurrence.In this study,internal extractive electrospray ionization mass spectrometry(i EESI-MS)was used to trace potential molecular tumor margins in lung cancer tissue.Molecular differential model for the determination of lung cancer tumor margin was established via partial least-squares discriminant analysis(PLS-DA)of iEESI-MS data collected from lung tissue pieces within cancer tumor area and iEESI-MS data collected from lung tissue pieces outside cancer tumor area.Proof-of-concept data demonstrate that the developed molecular differential model yields ca.1-2 mm wider potential molecular tumor margin of a lung cancer compared to the conventional histological analysis,showing promising potential of iEESI-MS to increase the accuracy of tumor margins determination and lower risk of lung cancer postoperative recurrence.Furthermore,our results revealed that creatine and taurine showed positive correlations with lung cancer.展开更多
In chemical science,the vertical ionization potential(VIP)is a crucial metric for understanding the electronegativity,hardness and softness of chemical material systems as well as the electronic structure and stabilit...In chemical science,the vertical ionization potential(VIP)is a crucial metric for understanding the electronegativity,hardness and softness of chemical material systems as well as the electronic structure and stability of molecules.Ever since the last century,the model chemistry composite methods have witnessed tremendous developments in computing the thermodynamic properties as well as the barrier heights.However,their performance in realm of the vertical electron processes of molecular systems has been rarely explored.In this study,we for the first time benchmarked the model chemistry composite methods(e.g.,CBS-QB3,G4 and W1BD)in comparison with the commonly used Koopmans's theorem(KT),electron propagator theory(e.g.,OVGF,D2,P3 and P3+)and CCSD(T)methods in calculating the VIP for up to 613 molecular systems with available experimental measurements.The large-scale test calculations strongly showed that the CBS-QB3 model chemistry composite technique can be well recommended to calculate VIP from the perspectives of accuracy,economy and applicability.Notably,the VIP values of up to 7 molecules were identified to have the absolute errors of larger than 0.3 e V at all calculation levels,which have strong hints that their VIP experimental values should be re-investigated.展开更多
In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. U...In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.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
Selenium is one of the important trace elements in the human body.Its deficiency will directly affect human health.With people's attention to health,the content of selenium in food has gradually attracted attentio...Selenium is one of the important trace elements in the human body.Its deficiency will directly affect human health.With people's attention to health,the content of selenium in food has gradually attracted attention.However,detecting selenium compounds in complex samples remains a challenge.In this work,we built an online heating-reaction device.This device combines the electrospray extraction ionization mass spectrometry(EESI-MS)with the heating reaction device,which can simultaneously detect various selenium compounds in complex liquid samples.Under acidic conditions,the sample was heated and catalyzed by a heating reaction device,so that the SeO~(2-)_(3)and O-phenylenediamine(OPD)could generate 1,3-dihydro-2,1,3-benzoselenadiazole.Based on the above reactions,we can detect organic selenium,inorganic selenium and other compounds in liquid samples by organic mass spectrometry.In this experiment,we determined the content of three forms of selenium:selenomethionine(SeMet),l-selenocystine(SeCys(2)),and sodium selenite.The calibration curves for SeMet,SeCys(2),and sodium selenite showed strong linearity within a range of 0.50-50.00μg/L.The limits of detection(LOD)for the three compounds were 0.22,0.27,and 0.41μg/L,respectively.The limits of quantification(LOQ)were 0.68,0.81,and 1.23μg/L,respectively.Spiked recoveries at three levels ranged from 98.8%to 106.1%.In addition,this method can simultaneously detect three selenium compounds and three other specific chemical components in tea infusion samples,providing a rapid and efficient method for identifying tea quality.展开更多
The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established th...The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established the relationship between the Rydberg state excitation(RSE) yields and the CPTC field parameters, such as field amplitude ratios and helicity of two components, the role of the relative phase(φ) in modulating RSE efficiency remains unclear. In this work, we theoretically investigate the φ dependence of RSE and ionization yields in the co-rotating and counter-rotating circularly polarized two-color(CPTC) few-cycle laser fields by a semiclassical model. We find that, in co-rotating CPTC fields, both RSE and ionization yields display pronounced oscillations as a function of φ and these oscillations are significantly suppressed in the counter-rotating configuration, particularly for ionization yields. Moreover, the ratio of RSE to ionization yields exhibits an out-of-phase oscillatory pattern between low-and high-intensity regimes. These results can be comprehended by the unique feature of φ dependence of CPTC few-cycle fields, based on our semiclassical analysis. Our results demonstrate that phase-controlled CPTC fields offer a versatile tool for steering ultrafast ionization and RSE dynamics of atoms and molecules.展开更多
This study analytically examines the ionization of atoms in strong near-circular laser fields.The classic Keldysh-Rutherford(KR)Coulomb-scattering(CS)model[Phys.Rev.Lett.121123201(2018)]successfully explained the atto...This study analytically examines the ionization of atoms in strong near-circular laser fields.The classic Keldysh-Rutherford(KR)Coulomb-scattering(CS)model[Phys.Rev.Lett.121123201(2018)]successfully explained the attoclock experimental curve for the H atom at lower laser intensities.Here,we develop a semiclassical model that includes the initial conditions related to the quantum properties of tunneling in the KR model at the beginning of the scattering process.This model is able to explain recent attoclock experimental curves over a wider range of laser and atomic parameters.Our results show the importance of system symmetry and quantum effects in attoclock measurements,suggesting the complex role of the Coulomb potential in strong-field ionization.展开更多
We demonstrate an all-optical technique for in situ monitoring of strong-field ionization(SFI)dynamics.The method relies on coherent scattering of a probe pulse from a transient plasma grating(TPG)formed by two interf...We demonstrate an all-optical technique for in situ monitoring of strong-field ionization(SFI)dynamics.The method relies on coherent scattering of a probe pulse from a transient plasma grating(TPG)formed by two interfering femtosecond pulses in a gas target.The diffracted signal provides a real-time,relative measure of the ionization yield.We demonstrate the method’s sensitivity by resolving the attosecond-scale coherent control of the ionization rate.Unlike conventional diagnostics that directly measure charged particles,our ensemble-based optical method is non-invasive and particularly suited for non-vacuum environments.To demonstrate its utility,we apply the technique to investigate the relationship between ionization and terahertz(THz)generation in a two-color(ω+2ω)field.We measure a phase offset of(0.18±0.05)π between the maxima of the ionization yield and the THz emission.This result provides a quantitative benchmark for theoretical models and establishes the TPG technique as a practical tool for probing SFI dynamics in ensemble systems.展开更多
We propose a method to characterize the features of a cold strontium cloud in a magneto-optical trap(MOT)through the photoionization of cold Sr atoms in a custom-designed reaction microscope.Sr atoms in the dark state...We propose a method to characterize the features of a cold strontium cloud in a magneto-optical trap(MOT)through the photoionization of cold Sr atoms in a custom-designed reaction microscope.Sr atoms in the dark state of 5s5p3P2 populated via the cascade transition 5s5p^(1)P_(1)→5s4d^(1)D_(2)→5s5p^(3)P_(2)accumulate a significant fraction,giving a long lifetime of 520 s.These atoms in the dark state are subsequently trapped by the gradient magnetic field of the MOT.By scanning the Sr+momentum distributions ionized with an 800 nm infrared femtosecond laser,we are able to outline the size of~0.55 mm in radius and the temperature of~0.40 mK for the dark-state atoms,which is significantly cooler than the MOT temperature of 3.3 mK trapped in the 461 nm.The size of MOT exhibits an oblate spheroidal distribution with a radius of approximately 0.35 mm and 0.55 mm,extracted with momenta of photoion and absorption imaging,respectively.The results using the photoion momenta are consistent with the expected results from absorption imaging,which confirms the method's reliability.The advantage of this method is the ability to simultaneously characterize the distribution information of atoms in different initial states within the cold atomic cloud.展开更多
The direct and dissociative ionizations of oxygen molecule are investigated experimen-tally by electron collision with energies from 350 eV to 8000 eV.The absolute ionization cross sections for the product ions(O_(2)^...The direct and dissociative ionizations of oxygen molecule are investigated experimen-tally by electron collision with energies from 350 eV to 8000 eV.The absolute ionization cross sections for the product ions(O_(2)^(2+),O_(2)^(2+)O^(+),O^(2+),and their total)and two Coulomb explosion channels(O^(+)+O^(+)and O^(2+)+O^(+))are obtained by putting the data of O^(2+)on the scale of Ar+from O_(2)and Ar gases mixed with a fixed relative flow ratio of 1:1.The experimental errors are assessed by taking uncertainties of various factors into account.The present absolute cross sections are well consistent with the previous data in the overlapped energy range below 1000 eV.展开更多
With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our resu...With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.展开更多
We investigated the nonsequential double ionization(NSDI)in Ar by two-color elliptically polarized laser field with a three-dimensional(3D)classical ensemble method.We study the relative phase effect of NSDI and disti...We investigated the nonsequential double ionization(NSDI)in Ar by two-color elliptically polarized laser field with a three-dimensional(3D)classical ensemble method.We study the relative phase effect of NSDI and distinguish two particular recollision channels in NSDI,which are recollision–impact ionization(RII)and recollision-induced excitation with subsequent ionization(RESI),according to the delay-time between the recollision and the final double ionization.The numerical results indicate that the ion momentum distribution is changed and the triangle structure is more obvious with the decrease of the relative phase.We also demonstrate that the RESI process always dominates in the whole double ionization process and the ratio of RESI and RII channels can be influenced by the relative phase.展开更多
An evaporation/condensation flow cell was developed and interfaced with the matrix-assisted laser desorption/ionization （MALDI） time-of-flight mass spectrometer for on-line bioaerosol detection and characterization,...An evaporation/condensation flow cell was developed and interfaced with the matrix-assisted laser desorption/ionization （MALDI） time-of-flight mass spectrometer for on-line bioaerosol detection and characterization, which allows matrix addition by condensation onto the laboratory-generated bioaerosol particles. The final coated particle exiting from the con- denser is then introduced into the aerodynamic particle sizer spectrometer or home-built aerosol laser time-of-flight mass spectrometer, and its aerodynamic size directly effects on the matrix-to-analyte molar ratio, which is very important for MALDI technique. In order to observe the protonated analyte molecular ion, and then determine the classification of bi- ological aerosols, the matrix-to-analyte molar ratio must be appropriate. Four experimental parameters, including the temperature of the heated reservoir, the initial particle size, its number concentration, and the matrix material, were tested experimentally to analyze their influences on the final particle size. This technique represents an on-line system of detection that has the potential to provide rapid and reliable identification of airborne biological aerosols.展开更多
The ginkgo terpenoids including bilobalide and ginkgolides are the main pharmaceutical components in the leaves or extracts of Ginkgo biloba L. In this paper, the analysis of bilobalide and ginkgolides in leaves of Gi...The ginkgo terpenoids including bilobalide and ginkgolides are the main pharmaceutical components in the leaves or extracts of Ginkgo biloba L. In this paper, the analysis of bilobalide and ginkgolides in leaves of Ginkgo biloba L. by high performance liquid chromatography (HPLC)-electrospray ionization (ESI)-mass spectrometry (MS) was carried out. The separation was performed on Inertsil ODS3 column with methanol-water (36:64) as mobile phase, with 1 mL·min -1 of flow rate at 35℃. Then the mass spectrum analysis was conducted by ZMD micromass electrospray ionization (ESI)-mass spectrometer (MS). The HPLC total ion chromatogram and selected ion chromatogram (with 325, 407, 423, 439 of m/z) of the sample and ESI-/MS mass spectra of the peaks in the chromatograms were obtained. So bilobalide, ginkgolide A, B, C and J in Ginkgo biloba L. leaves were identified. The method is easy and rapid, with a good accuracy.展开更多
Photon induced dissociation investigations of neutral tyramine and dopamine are carried out with synchrotron vacuum uRraviolet photoionization mass spectrometry and theoretical calculations. At low photon energy, only...Photon induced dissociation investigations of neutral tyramine and dopamine are carried out with synchrotron vacuum uRraviolet photoionization mass spectrometry and theoretical calculations. At low photon energy, only molecular ions are measured by virtue of nearthreshold photoionization. While increasing photon energy to 11.7 eV or more, four distinct fragment ions are obtained for tyramine and dopamine, respectively. Besides, the ionization energies of tyramine and dopamine are determined to be 7.984-0.05 and 7.674-0.05 eV by measuring the photoionization efficiency curves of corresponding molecular ions. With help of density function theory calculations, the detailed fragmentation pathways are established as well. These two molecular cations have similar aminoethyl group elimination pathways, CTHsO2＋ （m/z=124） and C7H8O＋ （m/z=108） are supposed to be generated by the McLafferty rearrangement via γ-hydrogen （7-H） shift inducing β-fission. And CH2NH2＋ is proposed to derive from the direct fission of C7-C8 bond. Besides, the McLafferty rearrangement and the C7-C8 bond fission are validated to be dominant dissociation pathways for tyramine and dopamine cations.展开更多
Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reag...Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer(CIMS)in the analysis of atmospheric ammonia.In this work,a vacuum ultraviolet(VUV)Kr lamp was used to replace the radioactive source,and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia.The ionization source is designed as a separated three-zone structure,and even 90 vol.%high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv.A signal normalization processing method was designed,and with this new method,the quantitative relative standard deviation(RSD)of the instrument was decreased from 17.5%to9.1%,and the coefficient of determination was increased from 0.8340 to 0.9856.The humidity correction parameters of the instrument were calculated from different humidity,and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters.The analytical time for a single sample is only 60 sec,and the limit of detection(LOD)was 8.59 pptv(signalto-noise ratio S/N=3).The ambient measurement made in Qingdao,China,in January 2021 with this newly designed CIMS,showed that the concentration of ammonia ranged from 1 to 130 ppbv.展开更多
基金supported by the National Special Fund for the Development of Major Research Equipment and Instrument(No.2020YFF01014503)the Young Taishan Scholars(No.tsqn201909039)the College 20 Project fromJi Nan Science&Technology Bureau(No.2021GXRC058).
文摘Formic and acetic acids are the most abundant gaseous organic acids and play the key role in the atmospheric chemistry.In iodine-adduct chemical ionizationmass spectrometry(CIMS),the low utilization efficiency of methyl iodide and humidity interference are two major issues of the vacuum ultraviolet(VUV)lamp initiated CIMS for on-line gaseous formic and acetic acids analysis.In this work,we present a new CIMS based on VUV lamp,and the ion-molecular reactor is separated into photoionization and chemical ionization zones by a reducer electrode.Acetone was added to the photoionization zone,and the VUV photoionization acetone provided low-energy electrons for methyl iodide to generate I−,and the addition of acetone reduced the amount of methyl iodide by 2/3.In the chemical ionization zone,a headspace vial containing ultrapure water was added for humidity calibration,and the vial changes the sensitivity as a function of humidity from ambiguity to well linear correlation(R2>0.95).With humidity calibration,the CIMS can quantitatively measure formic and acetic acids in the humidity range of 0%-88%RH.In this mode,limits of detection of 10 and 50 pptv are obtained for formic and acetic acids,respectively.And the relative standard deviation(RSD)of quantitation stability for 6 days were less than 10.5%.This CIMS was successfully used to determine the formic and acetic acids in the underground parking and ambient environment of the Shandong University campus(Qingdao,China).In addition,we developed a simple model based formic acid concentration to assess vehicular emissions.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0134200)the National Natural Science Foundation of China(Grant Nos.12474343,12174147,and 12074142)the Natural Science Foundation of Jilin Province,China(Grant No.20220101016JC)。
文摘Strong feld-induced nonsequential double ionization(NSDI)is a signifcant multi-electron phenomenon that provides crucial insights into understanding electron correlation and multiple ionization of atoms and molecules,but it is typically unattainable in a circularly polarized laser pulse,especially for long-wavelength lasers.We present evidence that NSDI can occur in the presence of a near-infrared or beyond laser pulse by introducing a bowtie-nanotip.The laser-induced local plasmon can alter the local ellipticity of the feld,thereby enabling NSDI through elliptical trajectories that facilitate recollisions with parent atoms.An oval-shaped momentum distribution of recoiled ions provides evidence for the modifcation of trajectories by the aligned nanotips.Our study introduces an innovative control knob to manipulate NSDI and electron dynamics through the utilization of nanostructures.
文摘We have conducted a two-color visible-ultraviolet （VIS-UV） resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron （PFI-PE） study of gaseous vana- dium mononitride （VN） in the total energy range of 56900-59020 cm-1. The VN molecules were selectively excited to single rotational levels of the intermediate VN（D3H0, v＇=0） state by using a VIS dye laser prior to photoionization by employing a UV laser. This two-color scheme allows the measurements of rovibronically selected and re- solved PFI-PE spectra for the VN＋（X2A; v＋=0, 1, and 2） ion vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J＋=3/2 is determined to be the lowest rotational level of the ground electronic state, indicating that the symmetry of the ground VN＋ electronic state is 2A3/2. The analysis of the PFI-PE spectra for VN＋ also yields accurate values for the adiabatic ionization energy for the formation of VN＋（X2A3/2）, IE（VN）=56909.5＋0.8 cm-1 （7.05588±0.00010 eV）, the vibrational fre- quency wc＋=1068.0±0.8 cm-1, the anharmonicity constant wc＋Xe＋=5.8±0.8 cm-1, the rotational constants Be＋=0.6563±0.0005 cm-1 and ae＋=0.0069±0.0004 cm-1, and the equi-librium bond length, re＋=1.529A, for VN＋（X2A3/2）; along with the rotational constants Bc＋=0.6578i0.0028 cm-1 and a＋=0.0085±0.0028 cm-1, and the equilibrium bond length re＋=1.527A for VN＋（X2As/2）, and the spin-orbit coupling constant A=153.3±0.8 cm-1 for VN＋（X2/k5/2,3/2）. The highly precise energetic and spectroscopic data obtained in the present study are valuable for benchmarking the predictions based on state-of-the-art ab initio quantum calculations.
基金supports by the National Natural Science Foundation of China(No.22174037)the Joint Funds of the Hunan Provincial Natural Science Foundation of China(No.2023JJ50255)+1 种基金Changsha Science and Technology Project(No.Z202269490128)National Key Research and Development Program of China(No.2023YFF0613400)are appreciated.
文摘Traditional electrospray ionization tandem mass spectrometry(ESI-MS^(n))has been a powerful tool in diverse research areas,however,it faces great limitations in the study of protein-small molecule interactions.In this article,the state-of-the-art temperature-controlled electrospray ionization tandem mass spectrometry(TC-ESI-MS^(n))is applied to investigate interactions between ubiquitin and two flavonol molecules,respectively.The combination of collision-induced dissociation(CID)and MS solution-melting experiments facilitates the understanding of flavonol-protein interactions in a new dimension across varying temperature ranges.While structural changes of proteins disturbed by small molecules are unseen in ESI-MS^(n),TC-ESI-MS^(n)allows a simultaneous assessment of the stability of the complex in both gas and liquid phases under various temperature conditions,meanwhile investigating the impact on the protein’s structure and tracking changes in thermodynamic data,and the characteristics of structural intermediates.
基金supported by Jiangxi Provincial International Science and Technology Cooperation Project(Nos.20203BDH80W010 and 20232BBH80012)the National Natural Science Foundation of China(Nos.82160410 and 81860379)+1 种基金Foundation of Jiangxi Provincial Department of Science and Technology(No.20212ACB206018)Key Research and Development Program of Jiangxi Province(No.20223BBG71009)。
文摘Accurate determination of lung cancer margins at the molecular level is of great significance to determine the optimal extent of resection during surgical operation and reduce the risk of postoperative recurrence.In this study,internal extractive electrospray ionization mass spectrometry(i EESI-MS)was used to trace potential molecular tumor margins in lung cancer tissue.Molecular differential model for the determination of lung cancer tumor margin was established via partial least-squares discriminant analysis(PLS-DA)of iEESI-MS data collected from lung tissue pieces within cancer tumor area and iEESI-MS data collected from lung tissue pieces outside cancer tumor area.Proof-of-concept data demonstrate that the developed molecular differential model yields ca.1-2 mm wider potential molecular tumor margin of a lung cancer compared to the conventional histological analysis,showing promising potential of iEESI-MS to increase the accuracy of tumor margins determination and lower risk of lung cancer postoperative recurrence.Furthermore,our results revealed that creatine and taurine showed positive correlations with lung cancer.
基金funded by the National Natural Science Foundation of China(Nos.22073069,21773082)Science Research Project of Hebei Education Department(No.QN2024255)。
文摘In chemical science,the vertical ionization potential(VIP)is a crucial metric for understanding the electronegativity,hardness and softness of chemical material systems as well as the electronic structure and stability of molecules.Ever since the last century,the model chemistry composite methods have witnessed tremendous developments in computing the thermodynamic properties as well as the barrier heights.However,their performance in realm of the vertical electron processes of molecular systems has been rarely explored.In this study,we for the first time benchmarked the model chemistry composite methods(e.g.,CBS-QB3,G4 and W1BD)in comparison with the commonly used Koopmans's theorem(KT),electron propagator theory(e.g.,OVGF,D2,P3 and P3+)and CCSD(T)methods in calculating the VIP for up to 613 molecular systems with available experimental measurements.The large-scale test calculations strongly showed that the CBS-QB3 model chemistry composite technique can be well recommended to calculate VIP from the perspectives of accuracy,economy and applicability.Notably,the VIP values of up to 7 molecules were identified to have the absolute errors of larger than 0.3 e V at all calculation levels,which have strong hints that their VIP experimental values should be re-investigated.
基金supported by the National Key R&D Program of China (Grant No. 2022YFF0503700)the special funds of Hubei Luojia Laboratory (220100011)+1 种基金Chao Xiong is supported by the ISSI-BJ project, “the electromagnetic data validation and scientific application research based on CSES satellite”ISSI/ISSI-BJ project “Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction”。
文摘In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.
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financially supported by Jiangxi University of Chinese Medicine School-level Science and Technology Innovation Team Development Program(No.CXTD22005)PhD research startup fund of Jiangxi University of Chinese Medicine(No.2023BSZR005)。
文摘Selenium is one of the important trace elements in the human body.Its deficiency will directly affect human health.With people's attention to health,the content of selenium in food has gradually attracted attention.However,detecting selenium compounds in complex samples remains a challenge.In this work,we built an online heating-reaction device.This device combines the electrospray extraction ionization mass spectrometry(EESI-MS)with the heating reaction device,which can simultaneously detect various selenium compounds in complex liquid samples.Under acidic conditions,the sample was heated and catalyzed by a heating reaction device,so that the SeO~(2-)_(3)and O-phenylenediamine(OPD)could generate 1,3-dihydro-2,1,3-benzoselenadiazole.Based on the above reactions,we can detect organic selenium,inorganic selenium and other compounds in liquid samples by organic mass spectrometry.In this experiment,we determined the content of three forms of selenium:selenomethionine(SeMet),l-selenocystine(SeCys(2)),and sodium selenite.The calibration curves for SeMet,SeCys(2),and sodium selenite showed strong linearity within a range of 0.50-50.00μg/L.The limits of detection(LOD)for the three compounds were 0.22,0.27,and 0.41μg/L,respectively.The limits of quantification(LOQ)were 0.68,0.81,and 1.23μg/L,respectively.Spiked recoveries at three levels ranged from 98.8%to 106.1%.In addition,this method can simultaneously detect three selenium compounds and three other specific chemical components in tea infusion samples,providing a rapid and efficient method for identifying tea quality.
基金supported by the National Natural Science Foundation of China (Nos. 12121004, 12274273, and 12450402)the Science and Technology Department of Hubei Province (No. 2020CFA029)+1 种基金CAS Project for Young Scientists in Basic Research (No. YSBR-091)the Youth Innovation Promotion Association CAS (No. 2021328)。
文摘The ultrafast excitation dynamics of atoms and molecules exposed to circularly polarized two-color(CPTC)laser fields constitute a fascinating topic in attosecond science. Although extensive research has established the relationship between the Rydberg state excitation(RSE) yields and the CPTC field parameters, such as field amplitude ratios and helicity of two components, the role of the relative phase(φ) in modulating RSE efficiency remains unclear. In this work, we theoretically investigate the φ dependence of RSE and ionization yields in the co-rotating and counter-rotating circularly polarized two-color(CPTC) few-cycle laser fields by a semiclassical model. We find that, in co-rotating CPTC fields, both RSE and ionization yields display pronounced oscillations as a function of φ and these oscillations are significantly suppressed in the counter-rotating configuration, particularly for ionization yields. Moreover, the ratio of RSE to ionization yields exhibits an out-of-phase oscillatory pattern between low-and high-intensity regimes. These results can be comprehended by the unique feature of φ dependence of CPTC few-cycle fields, based on our semiclassical analysis. Our results demonstrate that phase-controlled CPTC fields offer a versatile tool for steering ultrafast ionization and RSE dynamics of atoms and molecules.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12174239,12347165,and 12404330)Shaanxi Fundamental Science Research Project for Mathematics and Physics(Grant No.23JSY022)+2 种基金Natural Science Basic Research Program of Shaanxi(Grant No.2022JM-015)Hebei Natural Science Foundation(Grant No.A2022205002)Science and Technology Project of Hebei Education Department(Grant No.QN2022143)。
文摘This study analytically examines the ionization of atoms in strong near-circular laser fields.The classic Keldysh-Rutherford(KR)Coulomb-scattering(CS)model[Phys.Rev.Lett.121123201(2018)]successfully explained the attoclock experimental curve for the H atom at lower laser intensities.Here,we develop a semiclassical model that includes the initial conditions related to the quantum properties of tunneling in the KR model at the beginning of the scattering process.This model is able to explain recent attoclock experimental curves over a wider range of laser and atomic parameters.Our results show the importance of system symmetry and quantum effects in attoclock measurements,suggesting the complex role of the Coulomb potential in strong-field ionization.
基金supported by the NUDT Science Foundation for Indigenous Innovation(Grant No.24-ZZCX-ZXGC-15)the National Natural Science Foundation of China(Grant Nos.12234020,12450403,and 12374263)。
文摘We demonstrate an all-optical technique for in situ monitoring of strong-field ionization(SFI)dynamics.The method relies on coherent scattering of a probe pulse from a transient plasma grating(TPG)formed by two interfering femtosecond pulses in a gas target.The diffracted signal provides a real-time,relative measure of the ionization yield.We demonstrate the method’s sensitivity by resolving the attosecond-scale coherent control of the ionization rate.Unlike conventional diagnostics that directly measure charged particles,our ensemble-based optical method is non-invasive and particularly suited for non-vacuum environments.To demonstrate its utility,we apply the technique to investigate the relationship between ionization and terahertz(THz)generation in a two-color(ω+2ω)field.We measure a phase offset of(0.18±0.05)π between the maxima of the ionization yield and the THz emission.This result provides a quantitative benchmark for theoretical models and establishes the TPG technique as a practical tool for probing SFI dynamics in ensemble systems.
基金Project supported by the Natural Science Foundation of Henan(Grant No.252300421304)the National Natural Science Foundation of China(Grant Nos.12204498,12474259+1 种基金12334011)the National Key Research and Development Program of China(Grant No.2022YFA1604302)。
文摘We propose a method to characterize the features of a cold strontium cloud in a magneto-optical trap(MOT)through the photoionization of cold Sr atoms in a custom-designed reaction microscope.Sr atoms in the dark state of 5s5p3P2 populated via the cascade transition 5s5p^(1)P_(1)→5s4d^(1)D_(2)→5s5p^(3)P_(2)accumulate a significant fraction,giving a long lifetime of 520 s.These atoms in the dark state are subsequently trapped by the gradient magnetic field of the MOT.By scanning the Sr+momentum distributions ionized with an 800 nm infrared femtosecond laser,we are able to outline the size of~0.55 mm in radius and the temperature of~0.40 mK for the dark-state atoms,which is significantly cooler than the MOT temperature of 3.3 mK trapped in the 461 nm.The size of MOT exhibits an oblate spheroidal distribution with a radius of approximately 0.35 mm and 0.55 mm,extracted with momenta of photoion and absorption imaging,respectively.The results using the photoion momenta are consistent with the expected results from absorption imaging,which confirms the method's reliability.The advantage of this method is the ability to simultaneously characterize the distribution information of atoms in different initial states within the cold atomic cloud.
基金supported by the National Key Research and Development Program of China(No.2022YFA1602502)the National Natural Science Foundation of China(No.12127804).
文摘The direct and dissociative ionizations of oxygen molecule are investigated experimen-tally by electron collision with energies from 350 eV to 8000 eV.The absolute ionization cross sections for the product ions(O_(2)^(2+),O_(2)^(2+)O^(+),O^(2+),and their total)and two Coulomb explosion channels(O^(+)+O^(+)and O^(2+)+O^(+))are obtained by putting the data of O^(2+)on the scale of Ar+from O_(2)and Ar gases mixed with a fixed relative flow ratio of 1:1.The experimental errors are assessed by taking uncertainties of various factors into account.The present absolute cross sections are well consistent with the previous data in the overlapped energy range below 1000 eV.
基金supported by the National Natural Science Foundation of China (Grant No. 12074329)Nanhu Scholars Program for Young Scholars of Xinyang Normal University。
文摘With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.
基金Project supported by the National Natural Science Foundation of China(Grant No.61575077)the Natural Science Foundation of Jilin Province of China(Grant No.20180101225JC)
文摘We investigated the nonsequential double ionization(NSDI)in Ar by two-color elliptically polarized laser field with a three-dimensional(3D)classical ensemble method.We study the relative phase effect of NSDI and distinguish two particular recollision channels in NSDI,which are recollision–impact ionization(RII)and recollision-induced excitation with subsequent ionization(RESI),according to the delay-time between the recollision and the final double ionization.The numerical results indicate that the ion momentum distribution is changed and the triangle structure is more obvious with the decrease of the relative phase.We also demonstrate that the RESI process always dominates in the whole double ionization process and the ratio of RESI and RII channels can be influenced by the relative phase.
文摘An evaporation/condensation flow cell was developed and interfaced with the matrix-assisted laser desorption/ionization （MALDI） time-of-flight mass spectrometer for on-line bioaerosol detection and characterization, which allows matrix addition by condensation onto the laboratory-generated bioaerosol particles. The final coated particle exiting from the con- denser is then introduced into the aerodynamic particle sizer spectrometer or home-built aerosol laser time-of-flight mass spectrometer, and its aerodynamic size directly effects on the matrix-to-analyte molar ratio, which is very important for MALDI technique. In order to observe the protonated analyte molecular ion, and then determine the classification of bi- ological aerosols, the matrix-to-analyte molar ratio must be appropriate. Four experimental parameters, including the temperature of the heated reservoir, the initial particle size, its number concentration, and the matrix material, were tested experimentally to analyze their influences on the final particle size. This technique represents an on-line system of detection that has the potential to provide rapid and reliable identification of airborne biological aerosols.
文摘The ginkgo terpenoids including bilobalide and ginkgolides are the main pharmaceutical components in the leaves or extracts of Ginkgo biloba L. In this paper, the analysis of bilobalide and ginkgolides in leaves of Ginkgo biloba L. by high performance liquid chromatography (HPLC)-electrospray ionization (ESI)-mass spectrometry (MS) was carried out. The separation was performed on Inertsil ODS3 column with methanol-water (36:64) as mobile phase, with 1 mL·min -1 of flow rate at 35℃. Then the mass spectrum analysis was conducted by ZMD micromass electrospray ionization (ESI)-mass spectrometer (MS). The HPLC total ion chromatogram and selected ion chromatogram (with 325, 407, 423, 439 of m/z) of the sample and ESI-/MS mass spectra of the peaks in the chromatograms were obtained. So bilobalide, ginkgolide A, B, C and J in Ginkgo biloba L. leaves were identified. The method is easy and rapid, with a good accuracy.
基金Authors thank Dr. Yang Pan for useful discussions This work was supported by the National Natural Science Foundation of China （No.10805047）.
文摘Photon induced dissociation investigations of neutral tyramine and dopamine are carried out with synchrotron vacuum uRraviolet photoionization mass spectrometry and theoretical calculations. At low photon energy, only molecular ions are measured by virtue of nearthreshold photoionization. While increasing photon energy to 11.7 eV or more, four distinct fragment ions are obtained for tyramine and dopamine, respectively. Besides, the ionization energies of tyramine and dopamine are determined to be 7.984-0.05 and 7.674-0.05 eV by measuring the photoionization efficiency curves of corresponding molecular ions. With help of density function theory calculations, the detailed fragmentation pathways are established as well. These two molecular cations have similar aminoethyl group elimination pathways, CTHsO2＋ （m/z=124） and C7H8O＋ （m/z=108） are supposed to be generated by the McLafferty rearrangement via γ-hydrogen （7-H） shift inducing β-fission. And CH2NH2＋ is proposed to derive from the direct fission of C7-C8 bond. Besides, the McLafferty rearrangement and the C7-C8 bond fission are validated to be dominant dissociation pathways for tyramine and dopamine cations.
基金partially supported by the National Special Fund for the Development of Major Research Equipment and Instrument(No.2020YFF01014503)NSF of China(No.21874134)Young Taishan Scholars(No.tsqn201909039)
文摘Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer(CIMS)in the analysis of atmospheric ammonia.In this work,a vacuum ultraviolet(VUV)Kr lamp was used to replace the radioactive source,and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia.The ionization source is designed as a separated three-zone structure,and even 90 vol.%high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv.A signal normalization processing method was designed,and with this new method,the quantitative relative standard deviation(RSD)of the instrument was decreased from 17.5%to9.1%,and the coefficient of determination was increased from 0.8340 to 0.9856.The humidity correction parameters of the instrument were calculated from different humidity,and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters.The analytical time for a single sample is only 60 sec,and the limit of detection(LOD)was 8.59 pptv(signalto-noise ratio S/N=3).The ambient measurement made in Qingdao,China,in January 2021 with this newly designed CIMS,showed that the concentration of ammonia ranged from 1 to 130 ppbv.
