It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concen...It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concentrations of secondary organic aerosols(SOAs).In this study,we conducted a series of well-defined indoor chamber experiments to compare the effects of NO_(x)(NO and NO_(2))on the photooxidation of isomeric monoterpenes ofβ-pinene and limonene.For the photooxidation ofβ-pinene with NO_(x),the increase of the initial concentrations of NO([NO]_(0))shows a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a monotonous enhancement of the particle mass concentration.For the photooxidation of limonene with NO_(x),the increase of[NO]_(0) exhibits a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a parabolic trend of the particle mass concentration.Utilizing a newly developed vacuum ultraviolet free electron laser(VUV-FEL),the online threshold photoionization mass spectrometry reveals a series of novel compounds at molecular weight(MW)=232 and 306 for theβ-pinene+NO_(x) system and MW=187,261,280,and 306 for the limonene+NO_(x) system.The molecular structures and formation pathways of these species were inferred,which led to the prediction of the diversity and difference of SOA products(i.e.,ester and peroxide accretion products)formed from different monoterpene precursors.To improve the predictions of future air quality,it is recommended that climate models should incorporate the NO_(x)-driven diurnal photooxidation of monoterpenes for SOA formation mechanisms.展开更多
Elucidating the mutual effects between the different volatile organic compounds(VOCs)is crucial for comprehending the formation mechanism of atmospheric secondary organic aerosols(SOA).Here,the mixed VOCs experiments ...Elucidating the mutual effects between the different volatile organic compounds(VOCs)is crucial for comprehending the formation mechanism of atmospheric secondary organic aerosols(SOA).Here,the mixed VOCs experiments of isoprene and△^(3)-carene/β-caryophyllene were carried out in the presence of O_(3)using an indoor smog chamber.The suppression effect of isoprene was recognized by the scanning mobility particle sizer spectrometer,online vacuum ultraviolet free electron laser(VUV-FEL)photoionization aerosol mass spectrometry,and quantum chemical calculations.The results indicate that the suppression effect of isoprene on the ozonolysis of△^(3)-carene andβ-caryophyllene shows fluctuating and monotonous trends,respectively.The carbon content of the precursor could be themain factor for regulating the strength of the suppression effect.Plausible structures and formation mechanisms of several new products generated from the single VOC precursor and VOC-cross-reaction are proposed,which enrich the category of VOC oxidation products.Meanwhile,a new dimerization mechanism of the RO_(2)+R’O_(2)reaction is suggested,which offers an intriguing perspective on the gas phase formation process of particle phase accretion products.The present findings provide valuable insights into clarifying the pivotal roles played by isoprene in the interplay between different VOCs and understanding of SOA formation mechanisms of VOC mixtures,especially nearby the emission origins.展开更多
The oxygen evolution reaction(OER)is the bottleneck in the overall photocatalytic splitting of water.The active sites(terminal titanium or bridging oxygen)and active species(molecular or dissociative water)of the init...The oxygen evolution reaction(OER)is the bottleneck in the overall photocatalytic splitting of water.The active sites(terminal titanium or bridging oxygen)and active species(molecular or dissociative water)of the initial step of the photocatalyzed OER on the prototypical photocatalyst TiO_(2),remain debatable.Herein,the photocatalytic chemistry of monolayer water on oxygen-pretreated TiO_(2)(110)(o-TiO_(2)(110))and reduced TiO_(2)(110)(r-TiO_(2)(110))surfaces initiated by 400 nm light illumination was investigated by time-dependent two-photon photoemission spectroscopy(TD-2PPE).The photoinduced reduction of the H_(2)O/o-TiO_(2)(110)interface rather than the H2O/r-TiO_(2)(110)interface was detected by TD-2PPE.The difference in 2PPE originated from the presence of the terminal hydroxyl anions(OHt^(-))on H_(2)O/o-TiO_(2)(110),as identified by X-ray photoelectron spectroscopy and temperature-programmed desorption.Therefore,the evolution of the electronic structure of H_(2)O/o-TiO_(2)(110)was attributed to the photocatalyzed oxidation of the terminal hydroxyl anions,which most likely formed gaseous·OH radicals,reducing the interface.This work suggested that the oxidation of hydroxyl anions on top of the terminal titanium ions on TiO_(2),which were excluded previously in solution,need to be considered in the mechanistic studies of the photocatalyzed OER.展开更多
Here,we report the spin-orbit state-resolved differential cross sections(DCSs)for the prototype barrierless reaction S(^(1)D)+HD.Both product channels,namely H+SD(^(2)Π_(3/2,1/2))and D+SH(^(2)Π_(3/2,1/2)),were measu...Here,we report the spin-orbit state-resolved differential cross sections(DCSs)for the prototype barrierless reaction S(^(1)D)+HD.Both product channels,namely H+SD(^(2)Π_(3/2,1/2))and D+SH(^(2)Π_(3/2,1/2)),were measured by high-resolution crossed molecular beam experiments.The DCSs of the two product channels show an overall forward-backward symmetry,in accordance with statistical model predictions.However,the DCSs for different spin-orbit manifolds show different preferences in forward or backward scattering directions at the same collision energies.This study reveals that,even though the title reaction proceeds via the long-lived complex mechanism,the spin-orbit coupling effects in the product channels play an important role in the reaction process.展开更多
Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were ...Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were generat-ed with internal excitation by multiphoton photolysis of CHBr_(3)at 248 nm,and its rotational temperature was found to relax to the flow temperature in a few microseconds by colliding with bath gas.The relaxation rate coefficients for CH(X^(2)Π,v=0)radical in He,Ar,and N_(2)flow were obtained by time-resolved laser-induced fluorescence measurements,ranging from 10^(-12)cm^(3)·molecule^(-1)·s^(-1)to 10^(-11)cm^(3)·molecule^(-1)·s^(-1).The N_(2)flow exhibits the highest relax-ation rate for CH(X^(2)Π)radical due to its additional rovibrational levels,which allow for more efficient energy dissipation during collisions compared to monoatomic gases.The Ar flow shows a larger relaxation rate than He flow due to its greater polarizability and stronger long-range interaction with the CH(X^(2)Π)radical.展开更多
The photodissociation dynamics of polyatomic molecules is of great significance for the analysis of molecular potential energy surfaces and dissociation product channels.We studied the photodissociation dynamics of D_...The photodissociation dynamics of polyatomic molecules is of great significance for the analysis of molecular potential energy surfaces and dissociation product channels.We studied the photodissociation dynamics of D_(2)S^(+)in the ultraviolet region using the time-sliced velocity map ion imaging technique.The images of S+products were measured at photodissociation wavelengths around 340 nm.From these images,the total kinetic energy releases of the product,branching ratios,and angular distributions were derived.We found that the total kinetic energy releases and the angular anisotropy parameters of products generally showed similar characteristics.The D_(2) products are populated in v=0 and v=1 vibrational states,and the D_(2)(v=0)is predominantly populated at all the photolysis wavelengths.The angular distributions of S^(+)products are nearly isotropic at the photolysis wavelengths ranging from 340.10 nm to 340.34 nm.However,at the photodissociation wavelength of 340.39 nm,the angular distributions of S^(+)products were anisotropic.The change of angular distributions may result from different dissociation mechanisms involving nonadiabatic coupling and contribute to the final dissociation channel.This work provides a further understanding in the ultraviolet photodissociation dynamics of D_(2)S^(+)and more information on the isotopic effect for the photodissociation of the H_(2)S^(+)cation.展开更多
In the current work,we studied the infrared spectroscopy of neutral and cationic 2-ethoxyethanol(CH_(3)CH_(2)O CH_(2)CH_(2)OH,2-EE)using the infrared(IR)-vacuum-ultraviolet(VUV)non-resonant ionization and fragmenta-ti...In the current work,we studied the infrared spectroscopy of neutral and cationic 2-ethoxyethanol(CH_(3)CH_(2)O CH_(2)CH_(2)OH,2-EE)using the infrared(IR)-vacuum-ultraviolet(VUV)non-resonant ionization and fragmenta-tion detected IR spectroscopy(NRIFD-IR)technique.The spectral range was from 2700 cm^(−1)to 7250 cm^(−1).Upon radiation with a 118 nm laser,signals corresponding to the cationic 2-EE(m/z=90)and dissociative ioniza-tion products(m/z=72,59,46,and 45)were detected.The action IR spectra,derived from the signal variations of 2-EE and its fragments upon IR radiation,display differences,suggest-ing vibrational mode selectivity in the dissociative ionization process.To complement the ex-perimental findings,we performed density functional theory calculations at the B3LYP-D3(BJ)/def2-TZVPP level to determine the structures and anharmonic IR spectra of neutral and cationic 2-EE.The computed spectra showed good agreement with the experimental re-sults.展开更多
We report high-resolution velocity map imaging studies of S(^(1)D)atoms formed following excitation on two intense absorption bands of gas phase D_(2)S molecules,centred at wave-lengths~139.1 and~129.1 nm.DS–D bond f...We report high-resolution velocity map imaging studies of S(^(1)D)atoms formed following excitation on two intense absorption bands of gas phase D_(2)S molecules,centred at wave-lengths~139.1 and~129.1 nm.DS–D bond fission is the dominant fragmentation pathway at these wavelengths,yielding SD fragments in both the ground(X)and excited(A)electronic states.Most S(^(1)D)atoms arising via 21A′21A′the rival S atom elimination channel when exciting at~139.1 nm are formed with D_(2)partners,in a wide range of rovibrational levels.The partially resolved structure in the total translational energy distributions,P(ET),derived from the S(^(1)D)atom images,implies two dynamical routes into S(^(1)D)+D_(2)products following non-adiabatic coupling from the photo-excited Rydberg state to the dissociative potential energy surface(PES).Similar D_(2)products are evident in the P(ET)spectra derived from analysis of S(^(1)D)images from D_(2)S photolysis at~129.1 nm,but their contribution is overshadowed by a feature attributable to three-body dissociation to S(^(1)D)+2D fragments.These atomic products are deemed to arise via a natural extension of the dynamics responsible for the previously observed highly rotationally excited SD(A)fragments arising via the rival S–D bond fission pathway:asymmetric bond extension together with a dramatic opening of the interbond angle driven by torques generated after coupling to the highly anisotropic 2^(1)A′PES,leading to a centripetally-driven break-up.展开更多
We present a comprehensive investigation of the vibrational spectra and conformational distribution of neutral and cationic monoethanolamine(MEA)in the gas phase.Using infrared-vacuum ultraviolet non-resonant ionizati...We present a comprehensive investigation of the vibrational spectra and conformational distribution of neutral and cationic monoethanolamine(MEA)in the gas phase.Using infrared-vacuum ultraviolet non-resonant ionization fragmentation detected IR spectroscopy(NRIFD-IR),we obtained vibrational spectra in the 2500-3800 cm^(−1)range for both neutral and cationic MEA.Density functional theory(DFT)calculations at the B3LYPD3(BJ)/def2-TZVPP level were employed to elucidate the molecular structures and vibrational modes.Our analysis revealed twelve distinct conformers for neutral MEA,with N1gʹGgʹbeing the most stable,while cationic MEA exhibited four conformers,among which C1gʹGt conformer was found to be the primary contributor to the observed spectra.The experimental spectra were interpreted through comparison with anharmonic calculations,allowing for detailed assignment of vibrational modes.Notably,we observed significant differences in the OH stretch region between neutral and cationic species,reflecting changes in intramolecular hydrogen bonding upon ionization.Furthermore,our study highlights the necessity for distinct scaling factors when calculating harmonic frequencies for neutral and cationic substances.展开更多
OBJECTIVE: To assess the clinical curative effect of fuzi-cake-separated moxibustion at Zhongji(CV 3)and Guanyuan(CV 4) for preventing dysuria after internal fixation of lower limb fractures.METHODS: Sixty patients co...OBJECTIVE: To assess the clinical curative effect of fuzi-cake-separated moxibustion at Zhongji(CV 3)and Guanyuan(CV 4) for preventing dysuria after internal fixation of lower limb fractures.METHODS: Sixty patients conforming to the inclusion standards were randomly divided into a treatment group(n=30) and a control group(n=30).Fuzi-cake-separated moxibustion was performed at Guanyuan(CV 4) and Zhongji(CV 3), 20 min at a time, twice a day, for 3 days before operation in the treatment group. No fuzi-cake-separated moxibustion was performed in the control group. After treatment, the score for symptoms of first urination, urinary time, urinary volume, 24 h remaining urinary volume, incidence of uroschesis, and rate of controlling dysuria were compared to evaluate the curative effect of preventing post-operative dysuria.RESULTS: The score for symptoms of first urination,24 h remaining urinary volume(maximum 120 m L vs 250 m L, and less than 10 m L in 24 cases vs 15 cases), and the rate of controlling dysuria(83.34% vs30%) were significantly better(P<0.05, P<0.05, and P<0.001, respectively) in the treatment compared with the control group. There was no statistical difference(P>0.05) between the two groups in first post-operative urinary time, urinary volume, or incidence of 24 h uroschesis.CONCLUSION: Fuzi-cake-separated moxibustion at Zhongji(CV 3) and Guanyuan(CV 4) can better prevent post-operative dysuria, effectively promote the functional restoration of the urinary bladder,and control the incidence of post-operative dysuria.展开更多
Non-oxidative conversion of methane to olefins,aromatics and hydrogen(MTOAH) has been reported recently over metal single sites such as iron and platinum.The reaction was proposed to involve catalytic activation of me...Non-oxidative conversion of methane to olefins,aromatics and hydrogen(MTOAH) has been reported recently over metal single sites such as iron and platinum.The reaction was proposed to involve catalytic activation of methane followed by gas phase C-C coupling of methyl radicals.This study using H atom Rydberg Tagging time-of-flight technique provides direct experimental evidence for the formation of hydrogen radicals during MTOAH reaction over a catalytic quartz wall reactor containing embedded iron species(denoted as Fe-reactor).Fe-reactor gives 7.3% methane conversion at 1273 K with 41.2% selectivity toward C2(ethane,ethylene and acetylene) and 31.8% toward BTX(benzene,toluene and xylene),respectively.The enhancing effects of hydrogen radicals on overall MTOAH performance are validated by cofeeding hydrogen donor benzene,which provides an additional route of methane activation apart from catalytic activation.展开更多
α-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds.Molecular identification of key transient compounds during theα-pinene ozonolysis has been proven to be a c...α-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds.Molecular identification of key transient compounds during theα-pinene ozonolysis has been proven to be a challenging experimental target because of a large number of intermediates and products involved.Here we exploit the recently developed hybrid instruments that integrate aerosol mass spectrometry with a vacuum ultraviolet free-electron laser to study theα-pinene ozonolysis.The experiments ofα-pinene ozonolysis are performed in an indoor smog chamber,with reactor having a volume of 2 m^(3) which is made of fluorinated ethylene propylene film.Distinct mass spectral peaks provide direct experimental signatures of previously unseen compounds produced from the reaction ofα-pinene with O_(3).With the aid of quantum chemical calculations,plausible mechanisms for the formation of these new compounds are proposed.These findings provide crucial information on fundamental understanding of the initial steps ofα-pinene oxidation and the subsequent processes of new particle formation.展开更多
Ultraviolet photodissociation is a high-energy fast excitation method in mass spectrometry and has beensuccessfully applied for the elucidation of sequences and structures of biomolecules. However, its abilityto disti...Ultraviolet photodissociation is a high-energy fast excitation method in mass spectrometry and has beensuccessfully applied for the elucidation of sequences and structures of biomolecules. However, its abilityto distinguish the phosphorylation sites isomers of multi-phosphopeptides has been not systematicallyinvestigated until now. A 193-nm ultraviolet laser dissociation mass spectrometry system wasestablished in this study and applied to elucidate the complex multi-phosphorylation statuses mimickingthe functional regions of Sicl, Gli3 and Tau. The numbers of matched fragment ions and phosphorylationsite-determining ions were improved on average 123% and 104%, respectively, by utilizing the ultravioletphotodissociation strategy, comparing to the typically utilized collision induced dissociation strategy.Finally. 94% phosphorylation sites within various statuses were unambiguously elucidated.展开更多
Long-term fertilization and crop rotation can influence both organic C sequestration as well as the C composition of soils and the more resistant organic C compounds contained in humic acid(HA). This study examined th...Long-term fertilization and crop rotation can influence both organic C sequestration as well as the C composition of soils and the more resistant organic C compounds contained in humic acid(HA). This study examined the effects of fertilization and cropping type(monoculture corn(MC) and Kentucky bluegrass sod(KBS) and corn-oat-alfalfa-alfalfa rotation(RC)) on the HA composition of soil from a 52-year field study in southern Ontario, Canada. Humic acid samples were extracted from soil, and elemental analysis, infrared spectroscopy, solid state 13C nuclear magnetic resonance spectra, and electron paramagnetic resonance methods were used to determine the influence of the cropping type on the characteristics of HA. Both fertilization and cropping type affected the chemical characteristics of HA. Fertilization led to a 5.9% increase in C, a 7.6% decrease in O, and lower O/C and(N + O)/C ratios in HA as compared to the corresponding non-fertilized treatments. Rotation resulted in a lower proportion of C(48.1%) and a greater(N + O)/C ratio(0.7) relative to monoculture cropping. Infrared spectroscopy analysis showed that HA contained more C-O groups in fertilized soil than in non-fertilized soil under MC and KBS. Fertilization increased the O-alkyl-C, phenolic-C, and free radical contents of HA relative to non-fertilization treatments. Rotation decreased the aliphatic and carboxyl groups and increased the O-alkyl, carbohydrate, aryl, and phenolic groups and free radicals, relative to MC and KBS. Both long-term crop rotation and fertilization dramatically modified the soil HA composition. Significant relationships were observed between the molecular composition of HA and soil organic C. Hence, humic acid characterization could be used as an indicator of the long-term sustainability of crop management practices.展开更多
Elucidating the effects of anthropogenic pollutants on the photooxidation of biogenic volatile organic compounds is crucial to understanding the fundamental mechanisms of secondary organic aerosol(SOA)formation.Here,t...Elucidating the effects of anthropogenic pollutants on the photooxidation of biogenic volatile organic compounds is crucial to understanding the fundamental mechanisms of secondary organic aerosol(SOA)formation.Here,the impacts of NO_(2)and SO_(2)on SOA formation from the photooxidation of a representative monoterpene,β-pinene,were investigated by a number of laboratory studies.The results indicated NO_(2)enhanced the SOA mass concentrations and particle number concentrations under both low and highβ-pinene conditions.This could be rationalized that the increased O_(3)concentrations upon the NO_(x)photolysis was helpful for the generation of more amounts of O_(3)-oxidized products,which accelerated the SOA nucleation and growth.Combing with NO_(2),the promotion of the SOA yield by SO_(2)was mainly reflected in the increase of mass concentration,which might be due to the elimination of the newly formed particles by the initially formed particles.The observed low oxidation degree of SOA might be attributed to the fast growth of SOA,resulting in the uptake of less oxygenated gas-phase species onto the particle phase.The present findings have important implications for SOA formation affected by anthropogenic–biogenic interactions in the ambient atmosphere.展开更多
The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRI...The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRID-IR)method to study the molecular structure of neutral and cationic 2-methylallyl alcohol(MAA,CH_(2)=C(CH_(3))−CH_(2)−OH).Density functional theory calculations revealed five stable neutral and three stable cationic MAA conformers,respectively.Two neutral MAA conformers are expected to have an O−H…πintramolecular hydrogen bond interaction,based on the structural characterization that the OH group is directed toward the C=C double bond.The IR spectra of both neutral(2700−3700 cm^(−1))and cationic MAA(2500−7200 cm^(−1))were measured,and the anharmonic IR spectra were calculated at the B3LYP-D3(BJ)/def2-TZVPP level.The OH stretching vibration frequency of neutral MAA was observed at 3656 cm−1,slightly lower than those of methanol and ethanol.In contrast,the OH stretching vibration of cationic MAA was red-shifted by about 140 cm^(−1)compared to neutral MAA.The interaction region indicator and natural bond orbital analysis suggest that the O−H…πinteraction in neutral MAA is weak,and may not play a major role in stabilizing the neutral MAA.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22125303,92361302,92061203,22103082,22273101,22288201,and 21327901)the National Key Research and Development Program of China(No.2021YFA1400501)+3 种基金the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)Dalian Institute of Chemical Physics(No.DICPI202437)Chinese Academy of Sciences(No.GJJSTD20220001)the International Partnership Program of CAS(No.121421KYSB20170012)。
文摘It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concentrations of secondary organic aerosols(SOAs).In this study,we conducted a series of well-defined indoor chamber experiments to compare the effects of NO_(x)(NO and NO_(2))on the photooxidation of isomeric monoterpenes ofβ-pinene and limonene.For the photooxidation ofβ-pinene with NO_(x),the increase of the initial concentrations of NO([NO]_(0))shows a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a monotonous enhancement of the particle mass concentration.For the photooxidation of limonene with NO_(x),the increase of[NO]_(0) exhibits a monotonous suppression of the particle mass concentration,whereas the increase of[NO_(2)]_(0) shows a parabolic trend of the particle mass concentration.Utilizing a newly developed vacuum ultraviolet free electron laser(VUV-FEL),the online threshold photoionization mass spectrometry reveals a series of novel compounds at molecular weight(MW)=232 and 306 for theβ-pinene+NO_(x) system and MW=187,261,280,and 306 for the limonene+NO_(x) system.The molecular structures and formation pathways of these species were inferred,which led to the prediction of the diversity and difference of SOA products(i.e.,ester and peroxide accretion products)formed from different monoterpene precursors.To improve the predictions of future air quality,it is recommended that climate models should incorporate the NO_(x)-driven diurnal photooxidation of monoterpenes for SOA formation mechanisms.
基金supported by the National Natural Science Foundation of China(Nos.92361302,22125303,92061203,and 22288201)the National Key Research and Development Program of China(No.2021YFA1400501)+2 种基金the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)Dalian Institute of Chemical Physics(No.DICP DCLS201702)Chinese Academy of Sciences(No.GJJSTD20220001).
文摘Elucidating the mutual effects between the different volatile organic compounds(VOCs)is crucial for comprehending the formation mechanism of atmospheric secondary organic aerosols(SOA).Here,the mixed VOCs experiments of isoprene and△^(3)-carene/β-caryophyllene were carried out in the presence of O_(3)using an indoor smog chamber.The suppression effect of isoprene was recognized by the scanning mobility particle sizer spectrometer,online vacuum ultraviolet free electron laser(VUV-FEL)photoionization aerosol mass spectrometry,and quantum chemical calculations.The results indicate that the suppression effect of isoprene on the ozonolysis of△^(3)-carene andβ-caryophyllene shows fluctuating and monotonous trends,respectively.The carbon content of the precursor could be themain factor for regulating the strength of the suppression effect.Plausible structures and formation mechanisms of several new products generated from the single VOC precursor and VOC-cross-reaction are proposed,which enrich the category of VOC oxidation products.Meanwhile,a new dimerization mechanism of the RO_(2)+R’O_(2)reaction is suggested,which offers an intriguing perspective on the gas phase formation process of particle phase accretion products.The present findings provide valuable insights into clarifying the pivotal roles played by isoprene in the interplay between different VOCs and understanding of SOA formation mechanisms of VOC mixtures,especially nearby the emission origins.
基金supported by the National Key Research and Development Program of China(No.2021YFA1500601)the National Natural Science Foundation of China(Nos.22322306 and 22288201)+3 种基金the Chinese Academy of Sciences(Nos.YSBR007,XDB0970000)the Key Research Project of Shaanxi Provincial Science and Technology Department(No.2023-YBNY-158)the Xi’an Science and Technology Project(No.22NYYF016)the 111 Project。
文摘The oxygen evolution reaction(OER)is the bottleneck in the overall photocatalytic splitting of water.The active sites(terminal titanium or bridging oxygen)and active species(molecular or dissociative water)of the initial step of the photocatalyzed OER on the prototypical photocatalyst TiO_(2),remain debatable.Herein,the photocatalytic chemistry of monolayer water on oxygen-pretreated TiO_(2)(110)(o-TiO_(2)(110))and reduced TiO_(2)(110)(r-TiO_(2)(110))surfaces initiated by 400 nm light illumination was investigated by time-dependent two-photon photoemission spectroscopy(TD-2PPE).The photoinduced reduction of the H_(2)O/o-TiO_(2)(110)interface rather than the H2O/r-TiO_(2)(110)interface was detected by TD-2PPE.The difference in 2PPE originated from the presence of the terminal hydroxyl anions(OHt^(-))on H_(2)O/o-TiO_(2)(110),as identified by X-ray photoelectron spectroscopy and temperature-programmed desorption.Therefore,the evolution of the electronic structure of H_(2)O/o-TiO_(2)(110)was attributed to the photocatalyzed oxidation of the terminal hydroxyl anions,which most likely formed gaseous·OH radicals,reducing the interface.This work suggested that the oxidation of hydroxyl anions on top of the terminal titanium ions on TiO_(2),which were excluded previously in solution,need to be considered in the mechanistic studies of the photocatalyzed OER.
基金supported by the National Natural Science Foundation of China(Nos.92476207,22288201)the Chinese Academy of Sciences(No.XBD0970202)+2 种基金the Innovation Program for Quantum Science and Technology(No.2021ZD0303300)the Shenzhen Science and Technology Innovation Committee(No.20220814164755002)the Guangdong Innovative&Entrepreneurial Research Team Program(Nos.2019ZT08L455,2019JC01X091).
文摘Here,we report the spin-orbit state-resolved differential cross sections(DCSs)for the prototype barrierless reaction S(^(1)D)+HD.Both product channels,namely H+SD(^(2)Π_(3/2,1/2))and D+SH(^(2)Π_(3/2,1/2)),were measured by high-resolution crossed molecular beam experiments.The DCSs of the two product channels show an overall forward-backward symmetry,in accordance with statistical model predictions.However,the DCSs for different spin-orbit manifolds show different preferences in forward or backward scattering directions at the same collision energies.This study reveals that,even though the title reaction proceeds via the long-lived complex mechanism,the spin-orbit coupling effects in the product channels play an important role in the reaction process.
基金supported by the National Natural Science Foundation of China(No.22273103)the National Natural Science Foundation of China(NSFC Center for Chemical Dynamics)(No.22288201)+1 种基金Dalian Institute of Chemical Physics(DICP I202230)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(grant GJJSTD20220001)。
文摘Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were generat-ed with internal excitation by multiphoton photolysis of CHBr_(3)at 248 nm,and its rotational temperature was found to relax to the flow temperature in a few microseconds by colliding with bath gas.The relaxation rate coefficients for CH(X^(2)Π,v=0)radical in He,Ar,and N_(2)flow were obtained by time-resolved laser-induced fluorescence measurements,ranging from 10^(-12)cm^(3)·molecule^(-1)·s^(-1)to 10^(-11)cm^(3)·molecule^(-1)·s^(-1).The N_(2)flow exhibits the highest relax-ation rate for CH(X^(2)Π)radical due to its additional rovibrational levels,which allow for more efficient energy dissipation during collisions compared to monoatomic gases.The Ar flow shows a larger relaxation rate than He flow due to its greater polarizability and stronger long-range interaction with the CH(X^(2)Π)radical.
基金supported by the National Natural Science Foundation of China (Nos. 22125302, 22327801, and 92476107)the Innovation Program for Quantum Science and Technology (No.2021ZD0303304)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB0970103)the University of Science and Technology of China。
文摘The photodissociation dynamics of polyatomic molecules is of great significance for the analysis of molecular potential energy surfaces and dissociation product channels.We studied the photodissociation dynamics of D_(2)S^(+)in the ultraviolet region using the time-sliced velocity map ion imaging technique.The images of S+products were measured at photodissociation wavelengths around 340 nm.From these images,the total kinetic energy releases of the product,branching ratios,and angular distributions were derived.We found that the total kinetic energy releases and the angular anisotropy parameters of products generally showed similar characteristics.The D_(2) products are populated in v=0 and v=1 vibrational states,and the D_(2)(v=0)is predominantly populated at all the photolysis wavelengths.The angular distributions of S^(+)products are nearly isotropic at the photolysis wavelengths ranging from 340.10 nm to 340.34 nm.However,at the photodissociation wavelength of 340.39 nm,the angular distributions of S^(+)products were anisotropic.The change of angular distributions may result from different dissociation mechanisms involving nonadiabatic coupling and contribute to the final dissociation channel.This work provides a further understanding in the ultraviolet photodissociation dynamics of D_(2)S^(+)and more information on the isotopic effect for the photodissociation of the H_(2)S^(+)cation.
基金funded by the National Natural Science Foundation of China(No.22288201)the Chinese Academy of Sciences(GJJSTD20220001)the Innovation Program for Quantum Science and Technology(No.2021ZD0303305)。
文摘In the current work,we studied the infrared spectroscopy of neutral and cationic 2-ethoxyethanol(CH_(3)CH_(2)O CH_(2)CH_(2)OH,2-EE)using the infrared(IR)-vacuum-ultraviolet(VUV)non-resonant ionization and fragmenta-tion detected IR spectroscopy(NRIFD-IR)technique.The spectral range was from 2700 cm^(−1)to 7250 cm^(−1).Upon radiation with a 118 nm laser,signals corresponding to the cationic 2-EE(m/z=90)and dissociative ioniza-tion products(m/z=72,59,46,and 45)were detected.The action IR spectra,derived from the signal variations of 2-EE and its fragments upon IR radiation,display differences,suggest-ing vibrational mode selectivity in the dissociative ionization process.To complement the ex-perimental findings,we performed density functional theory calculations at the B3LYP-D3(BJ)/def2-TZVPP level to determine the structures and anharmonic IR spectra of neutral and cationic 2-EE.The computed spectra showed good agreement with the experimental re-sults.
基金supported by the National Natural Science Foundation of China(Nos.22241304,22225303,22403091,22173100)the Major Program of the National Natural Science Foundation of China(Nos.42494850 and 42494853)+5 种基金the National Natural Science Foundation of China(NSFC Center for Chemical Dynamics(No.22288201))the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB0970000 and XDB0970200)the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)the Liaoning Revitalization Talents Program(No.XLYC2402046)the Shenzhen Science and Technology Program(No.ZDSYS20200421111001787)Zhenxing Li thanks the Guangdong Science and Technology Program(No.2025A1515012671)。
文摘We report high-resolution velocity map imaging studies of S(^(1)D)atoms formed following excitation on two intense absorption bands of gas phase D_(2)S molecules,centred at wave-lengths~139.1 and~129.1 nm.DS–D bond fission is the dominant fragmentation pathway at these wavelengths,yielding SD fragments in both the ground(X)and excited(A)electronic states.Most S(^(1)D)atoms arising via 21A′21A′the rival S atom elimination channel when exciting at~139.1 nm are formed with D_(2)partners,in a wide range of rovibrational levels.The partially resolved structure in the total translational energy distributions,P(ET),derived from the S(^(1)D)atom images,implies two dynamical routes into S(^(1)D)+D_(2)products following non-adiabatic coupling from the photo-excited Rydberg state to the dissociative potential energy surface(PES).Similar D_(2)products are evident in the P(ET)spectra derived from analysis of S(^(1)D)images from D_(2)S photolysis at~129.1 nm,but their contribution is overshadowed by a feature attributable to three-body dissociation to S(^(1)D)+2D fragments.These atomic products are deemed to arise via a natural extension of the dynamics responsible for the previously observed highly rotationally excited SD(A)fragments arising via the rival S–D bond fission pathway:asymmetric bond extension together with a dramatic opening of the interbond angle driven by torques generated after coupling to the highly anisotropic 2^(1)A′PES,leading to a centripetally-driven break-up.
基金the Dalian Coherent Light Source (DCLS) for support and assistancesurported by the National Natural Science Foundation of China (No.22288201)+1 种基金the Chinese Academy of Sciences (GJJSTD20220001)the Innovation Program for Quantum Science and Technology (No.2021ZD0303305)。
文摘We present a comprehensive investigation of the vibrational spectra and conformational distribution of neutral and cationic monoethanolamine(MEA)in the gas phase.Using infrared-vacuum ultraviolet non-resonant ionization fragmentation detected IR spectroscopy(NRIFD-IR),we obtained vibrational spectra in the 2500-3800 cm^(−1)range for both neutral and cationic MEA.Density functional theory(DFT)calculations at the B3LYPD3(BJ)/def2-TZVPP level were employed to elucidate the molecular structures and vibrational modes.Our analysis revealed twelve distinct conformers for neutral MEA,with N1gʹGgʹbeing the most stable,while cationic MEA exhibited four conformers,among which C1gʹGt conformer was found to be the primary contributor to the observed spectra.The experimental spectra were interpreted through comparison with anharmonic calculations,allowing for detailed assignment of vibrational modes.Notably,we observed significant differences in the OH stretch region between neutral and cationic species,reflecting changes in intramolecular hydrogen bonding upon ionization.Furthermore,our study highlights the necessity for distinct scaling factors when calculating harmonic frequencies for neutral and cationic substances.
基金supported by the National Key Research and Development Program of(No.2021YFA1500601 and No.2018YFA0208703)the National Natural Science Foundation of China(No.21973010 and No.21973092)+3 种基金the Instrument Developing Project of the Chinese Academy of Sciences(No.YZ201504)the CAS Projects for Young Scientists in Basic Research(No.YSBR-007)the Dalian Institute of Chemical Physics Innovation Foundation(DICP I202205)LiaoNing Revitalization Talents Program(No.XLYC1907032).
基金supported by the National Natural Sci-ence Foundation of China(No.21973092 and No.21873004)the National Key Research and Develop-ment Program of China(No.2018YFA0208703)+1 种基金Chinese Academy of Sciences(YSBR-007)Dalian In-stitute of Chemical Physics(DICP I202205).
基金Supported by Shaoxing's Science and Technology Plan(No.2012D10020):Clinical research of fuzi-cake-separated moxibustion for preventing dysuria after operation for fracture
文摘OBJECTIVE: To assess the clinical curative effect of fuzi-cake-separated moxibustion at Zhongji(CV 3)and Guanyuan(CV 4) for preventing dysuria after internal fixation of lower limb fractures.METHODS: Sixty patients conforming to the inclusion standards were randomly divided into a treatment group(n=30) and a control group(n=30).Fuzi-cake-separated moxibustion was performed at Guanyuan(CV 4) and Zhongji(CV 3), 20 min at a time, twice a day, for 3 days before operation in the treatment group. No fuzi-cake-separated moxibustion was performed in the control group. After treatment, the score for symptoms of first urination, urinary time, urinary volume, 24 h remaining urinary volume, incidence of uroschesis, and rate of controlling dysuria were compared to evaluate the curative effect of preventing post-operative dysuria.RESULTS: The score for symptoms of first urination,24 h remaining urinary volume(maximum 120 m L vs 250 m L, and less than 10 m L in 24 cases vs 15 cases), and the rate of controlling dysuria(83.34% vs30%) were significantly better(P<0.05, P<0.05, and P<0.001, respectively) in the treatment compared with the control group. There was no statistical difference(P>0.05) between the two groups in first post-operative urinary time, urinary volume, or incidence of 24 h uroschesis.CONCLUSION: Fuzi-cake-separated moxibustion at Zhongji(CV 3) and Guanyuan(CV 4) can better prevent post-operative dysuria, effectively promote the functional restoration of the urinary bladder,and control the incidence of post-operative dysuria.
基金supported by the Chinese Academy of Sciences (XDB10020202)the National Natural Science Foundation of China (Grant Nos. 21621063, 21425312, 21761132035)the National Key R&D Program of China (2017YFA0403402)。
文摘Non-oxidative conversion of methane to olefins,aromatics and hydrogen(MTOAH) has been reported recently over metal single sites such as iron and platinum.The reaction was proposed to involve catalytic activation of methane followed by gas phase C-C coupling of methyl radicals.This study using H atom Rydberg Tagging time-of-flight technique provides direct experimental evidence for the formation of hydrogen radicals during MTOAH reaction over a catalytic quartz wall reactor containing embedded iron species(denoted as Fe-reactor).Fe-reactor gives 7.3% methane conversion at 1273 K with 41.2% selectivity toward C2(ethane,ethylene and acetylene) and 31.8% toward BTX(benzene,toluene and xylene),respectively.The enhancing effects of hydrogen radicals on overall MTOAH performance are validated by cofeeding hydrogen donor benzene,which provides an additional route of methane activation apart from catalytic activation.
基金financially supported by the National Natural Science Foundation of China(No.22125303,No.92061203,and No.21688102)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17000000)+2 种基金Dalian Institute of Chemical Physics(DICP DCLS201701)Chinese Academy of Sciences(No.GJJSTD20190002)K.C.Wong Education Foundation(No.GJTD-2018-06)。
文摘α-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds.Molecular identification of key transient compounds during theα-pinene ozonolysis has been proven to be a challenging experimental target because of a large number of intermediates and products involved.Here we exploit the recently developed hybrid instruments that integrate aerosol mass spectrometry with a vacuum ultraviolet free-electron laser to study theα-pinene ozonolysis.The experiments ofα-pinene ozonolysis are performed in an indoor smog chamber,with reactor having a volume of 2 m^(3) which is made of fluorinated ethylene propylene film.Distinct mass spectral peaks provide direct experimental signatures of previously unseen compounds produced from the reaction ofα-pinene with O_(3).With the aid of quantum chemical calculations,plausible mechanisms for the formation of these new compounds are proposed.These findings provide crucial information on fundamental understanding of the initial steps ofα-pinene oxidation and the subsequent processes of new particle formation.
基金supported by the National Natural Science Foundation of China(No.22103023,No.22173040,No.22241301,No.22103032,No.22173042,and No.21973037)the Shenzhen Science and Technology Innovation Committee(No.ZDSYS20200421111001787,No.JCYJ20210324103810029,No.20220815145746004,and No.2021344670)+1 种基金the Guangdong Innovative&Entrepreneurial Research Team Program(No.2019ZT08L455 and No.2019JC01X091)Innovation Program for Quantum Science and Technology(No.2021ZD0303304).
基金Financial supports are gratefully acknowledged for the China State Key Research Grant(No.2016YFF0200504)China State Key Basic Research Program Grant(No.2013CB911203)+2 种基金the National Natural Science Foundation of China(No.21675152)the Youth Innovation Promotion Association CAS(No.2014164)grant from DICP(No.ZZBS201603)
文摘Ultraviolet photodissociation is a high-energy fast excitation method in mass spectrometry and has beensuccessfully applied for the elucidation of sequences and structures of biomolecules. However, its abilityto distinguish the phosphorylation sites isomers of multi-phosphopeptides has been not systematicallyinvestigated until now. A 193-nm ultraviolet laser dissociation mass spectrometry system wasestablished in this study and applied to elucidate the complex multi-phosphorylation statuses mimickingthe functional regions of Sicl, Gli3 and Tau. The numbers of matched fragment ions and phosphorylationsite-determining ions were improved on average 123% and 104%, respectively, by utilizing the ultravioletphotodissociation strategy, comparing to the typically utilized collision induced dissociation strategy.Finally. 94% phosphorylation sites within various statuses were unambiguously elucidated.
基金supported by the National Natural Science Foundation of China (No. 41571317)the Natural Science Foundation of Guangdong Province, China (No. 2018 A030313940)the Twelfth Five-Year National Science and Technology Support Project for Cycling of Agricultural Science and Technology Project, China (No. 2012BAD14B00)。
文摘Long-term fertilization and crop rotation can influence both organic C sequestration as well as the C composition of soils and the more resistant organic C compounds contained in humic acid(HA). This study examined the effects of fertilization and cropping type(monoculture corn(MC) and Kentucky bluegrass sod(KBS) and corn-oat-alfalfa-alfalfa rotation(RC)) on the HA composition of soil from a 52-year field study in southern Ontario, Canada. Humic acid samples were extracted from soil, and elemental analysis, infrared spectroscopy, solid state 13C nuclear magnetic resonance spectra, and electron paramagnetic resonance methods were used to determine the influence of the cropping type on the characteristics of HA. Both fertilization and cropping type affected the chemical characteristics of HA. Fertilization led to a 5.9% increase in C, a 7.6% decrease in O, and lower O/C and(N + O)/C ratios in HA as compared to the corresponding non-fertilized treatments. Rotation resulted in a lower proportion of C(48.1%) and a greater(N + O)/C ratio(0.7) relative to monoculture cropping. Infrared spectroscopy analysis showed that HA contained more C-O groups in fertilized soil than in non-fertilized soil under MC and KBS. Fertilization increased the O-alkyl-C, phenolic-C, and free radical contents of HA relative to non-fertilization treatments. Rotation decreased the aliphatic and carboxyl groups and increased the O-alkyl, carbohydrate, aryl, and phenolic groups and free radicals, relative to MC and KBS. Both long-term crop rotation and fertilization dramatically modified the soil HA composition. Significant relationships were observed between the molecular composition of HA and soil organic C. Hence, humic acid characterization could be used as an indicator of the long-term sustainability of crop management practices.
基金National Natural Science Foundation of China (Nos.22125303,92061203,and 22288201)the National Key Research and Development Program of China (No.2021YFA1400501)+3 种基金Innovation Program for Quantum Science and Technology (No.2021ZD0303304)Dalian Institute of Chemical Physics (No.DICP DCLS201702)Chinese Academy of Sciences (No.GJJSTD20220001)K.C.Wong Education Foundation (No.GJTD-2018-06)。
文摘Elucidating the effects of anthropogenic pollutants on the photooxidation of biogenic volatile organic compounds is crucial to understanding the fundamental mechanisms of secondary organic aerosol(SOA)formation.Here,the impacts of NO_(2)and SO_(2)on SOA formation from the photooxidation of a representative monoterpene,β-pinene,were investigated by a number of laboratory studies.The results indicated NO_(2)enhanced the SOA mass concentrations and particle number concentrations under both low and highβ-pinene conditions.This could be rationalized that the increased O_(3)concentrations upon the NO_(x)photolysis was helpful for the generation of more amounts of O_(3)-oxidized products,which accelerated the SOA nucleation and growth.Combing with NO_(2),the promotion of the SOA yield by SO_(2)was mainly reflected in the increase of mass concentration,which might be due to the elimination of the newly formed particles by the initially formed particles.The observed low oxidation degree of SOA might be attributed to the fast growth of SOA,resulting in the uptake of less oxygenated gas-phase species onto the particle phase.The present findings have important implications for SOA formation affected by anthropogenic–biogenic interactions in the ambient atmosphere.
基金gratefully acknowledge the Dalian Coherent Light Source(DCLS)for support and assistanceThis work was supported by the National Natural Science Foundation of China(No.22288201)+1 种基金the Chinese Academy of Sciences(GJJSTD20220001)the Innovation Program for Quantum Science and Technology(No.2021ZD0303305).
文摘The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRID-IR)method to study the molecular structure of neutral and cationic 2-methylallyl alcohol(MAA,CH_(2)=C(CH_(3))−CH_(2)−OH).Density functional theory calculations revealed five stable neutral and three stable cationic MAA conformers,respectively.Two neutral MAA conformers are expected to have an O−H…πintramolecular hydrogen bond interaction,based on the structural characterization that the OH group is directed toward the C=C double bond.The IR spectra of both neutral(2700−3700 cm^(−1))and cationic MAA(2500−7200 cm^(−1))were measured,and the anharmonic IR spectra were calculated at the B3LYP-D3(BJ)/def2-TZVPP level.The OH stretching vibration frequency of neutral MAA was observed at 3656 cm−1,slightly lower than those of methanol and ethanol.In contrast,the OH stretching vibration of cationic MAA was red-shifted by about 140 cm^(−1)compared to neutral MAA.The interaction region indicator and natural bond orbital analysis suggest that the O−H…πinteraction in neutral MAA is weak,and may not play a major role in stabilizing the neutral MAA.
