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
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
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
Dissociative adsorption of HCl on Au(111)has become one of unsolved puzzles in surface chemistry.Despite tremendous efforts in the past years,varioustheoretical models still greatly overestimate the zero-coverage init...Dissociative adsorption of HCl on Au(111)has become one of unsolved puzzles in surface chemistry.Despite tremendous efforts in the past years,varioustheoretical models still greatly overestimate the zero-coverage initial sticking probabilities(So).To find the origin of the large experiment-theory discrepancy,we have revisited the dissociative adsorption of HCl on Au(111)with a newly designed molecular beam-surface apparatus.The zero-coverage So derived from Cl-coverage measurements with varying HCl doses agree well with previous ones.However,we notice a sharp change of the coverage/dose slope with the HCl dosage at the low coverage regime,which may result in some uncertainties to the fitted So value.This seems consistent with a coverage-dependence of the dissociation barrier predicted by density functional theory at low Cl-coverages.Our results reveal the potential inconsistency of utilizing simulations with finite coverage to compare against experimental data with zero coverage in this system,and provide guidance for improving both experiment and theory in this regard.展开更多
The F+H_(2)reaction has long been a benchmark system in reaction dynamics.We report here a combined experimental and theoretical study on the F+H_(2)(v=1,j=1)reaction at a collision energy of 0.62 kcal/mol.The rotatio...The F+H_(2)reaction has long been a benchmark system in reaction dynamics.We report here a combined experimental and theoretical study on the F+H_(2)(v=1,j=1)reaction at a collision energy of 0.62 kcal/mol.The rotational state-resolved differential cross sections(DCSs)as well as the integral cross sections(ICSs)were obtained by the crossed beam experiment and the quantum dynamical calculation.It is found that the rotationally excited state F+H_(2)(v=1,j=1)reaction produces rotationally hotter but vibrationally colder products,compared with the rotational ground state reaction at the same total energy.The stereodynamics of the F+H_(2)(v=1,j=1)reaction is also analyzed theoretically,showing that minor differences exist for the reactants initially prepared in different spatial alignments.展开更多
3-Furfural(C_(5)H_(4)O_(2))is a furan(C_(4)H_(4)O)derivative compound formed by replacing the hydrogen(H)atom at the ring 3-position with the aldehyde(CHO)group substituent.In this work,we intend to investigate the ul...3-Furfural(C_(5)H_(4)O_(2))is a furan(C_(4)H_(4)O)derivative compound formed by replacing the hydrogen(H)atom at the ring 3-position with the aldehyde(CHO)group substituent.In this work,we intend to investigate the ultrafast decay dynamics of electronically excited 3-furfural using the femtosecond time-resolved photoelectron imaging technique.At pump wavelengths of 259.5,238.6 and 218.311m,two alternative decay mechanisms for the S_(2)(^(1)ππ*)state are tentatively proposed and discussed.Specifically,we prefer to suggest that a fraction of the initially prepared wavepacket in the S_(2)(^(1)ππ*)state is likely to undergo the subpicosecond relaxation via the S_(1)(^(1)nπ*)state.Presumably the lower lying T_(2)(^(3)ππ*)state is subsequently populated on a∼4 ps timescale via intersystem crossing from the minimum of the S_(1)(^(1)nπ*)state surface.The relaxation of the T_(2)(^(3)ππ*)state is sensitive to its vibrational excess energy and the value of its lifetime is 1.6±0.2 ns,280±30 ps and 50±10 ps for pump wavelengths of 259.5,238.6 and 218.3 m,respectively.展开更多
Time-sliced velocity map ion imaging(VMI)experiments were performed to investigate the photodissociation of H_(2)S^(+)X^(2)B_(1),via the excitation to the A^(2)A_(1)(0,11,0)state.Experimental images of the S^(+)(^(4)S...Time-sliced velocity map ion imaging(VMI)experiments were performed to investigate the photodissociation of H_(2)S^(+)X^(2)B_(1),via the excitation to the A^(2)A_(1)(0,11,0)state.Experimental images of the S^(+)(^(4)Su)products were recorded near 349.60 nm for the K=1 band,and near 344.30 nm for the K=2 band.The derived product total kinetic energy release(TKER)spectra exhibit partially rotationally resolved structures corresponding to the H_(2)(X^(1)∑_(g)^(+))co-products.The observed product state and angular distributions both exhibit sensitive dependence on the photolysis wavelength at near 349.60 nm and 344.30 nm.These phenomena indicate the underlying rich dynamic details and the role of the rotational excitation of H_(2)S^(+).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
The prototypical reaction of F+HD→DF+H was investigated at collision energies from 3.03 meV to 17.97 meV using a crossed molecular beam apparatus with multichannel Rydberg tagging time-of-flight detection.Significant...The prototypical reaction of F+HD→DF+H was investigated at collision energies from 3.03 meV to 17.97 meV using a crossed molecular beam apparatus with multichannel Rydberg tagging time-of-flight detection.Significant contributions from both the BornOppenheimer(BO)forbidden reaction F^(*)(^(2)P_(1/2))+HD→DF+H and the BO-allowed reaction F(^(2)P_(3/2))+HD→DF+H were observed.In the backward scattering direction,the contribution from the BO-forbidden reaction F^(*)(^(2)P_(1/2))+HD was found to be considerably greater than the BO-allowed reaction F(^(2)P_(3/2))+HD,indicating the non-adiabatic effects play an important role in the dynamics of the title reaction at low collision energies.Collision-energy dependence of differential cross sections(DCSs)in the backward scattering direction was found to be monotonously decreased as the collision energy decreases,which does not support the existence of resonance states in this energy range.DCSs of both BO-allowed and BO-forbidden reactions were measured at seven collision energies from 3.03 meV to 17.97 meV.It is quite unexpected that the angular distribution gradually shifts from backward to sideway as the collision energy decreases from 17.97 meV to 3.03 meV,suggesting some unknown mechanisms may exist at low collision energies.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.
基金supported by the National Natural Science Foundation of China(No.22173042,No.21973037,No.22073089,and No.22327801)the In-novation program for Quantum Science and Technolo-gy(No.2021ZD0303304)+2 种基金the Guangdong Science and Technology Program(No.2019ZT08L455 and No.2019JC01X091)the Shenzhen Science and Technology Program(No.ZDSYS2020421111001787)Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0450101).
文摘Dissociative adsorption of HCl on Au(111)has become one of unsolved puzzles in surface chemistry.Despite tremendous efforts in the past years,varioustheoretical models still greatly overestimate the zero-coverage initial sticking probabilities(So).To find the origin of the large experiment-theory discrepancy,we have revisited the dissociative adsorption of HCl on Au(111)with a newly designed molecular beam-surface apparatus.The zero-coverage So derived from Cl-coverage measurements with varying HCl doses agree well with previous ones.However,we notice a sharp change of the coverage/dose slope with the HCl dosage at the low coverage regime,which may result in some uncertainties to the fitted So value.This seems consistent with a coverage-dependence of the dissociation barrier predicted by density functional theory at low Cl-coverages.Our results reveal the potential inconsistency of utilizing simulations with finite coverage to compare against experimental data with zero coverage in this system,and provide guidance for improving both experiment and theory in this regard.
基金the National Natural Science Foundation of China(Nos.22288201,22173040,22241301,22103032)the Chinese Academy of Sciences(No.GJJSTD20220001),the Innovation Program for Quantum Scienceand Technology(No.2021ZD0303300)+2 种基金the Guangdong Science and Technology Program(Nos.2019ZT08L455,2019JC01X091)the Shenzhen Science and Technology Innovation Committee(Nos.JCYJ20210324103810029,20220815145746004,and 2021344670)the Shenzhen Science and Technology Program(No.DSYS20200421111001787).
文摘The F+H_(2)reaction has long been a benchmark system in reaction dynamics.We report here a combined experimental and theoretical study on the F+H_(2)(v=1,j=1)reaction at a collision energy of 0.62 kcal/mol.The rotational state-resolved differential cross sections(DCSs)as well as the integral cross sections(ICSs)were obtained by the crossed beam experiment and the quantum dynamical calculation.It is found that the rotationally excited state F+H_(2)(v=1,j=1)reaction produces rotationally hotter but vibrationally colder products,compared with the rotational ground state reaction at the same total energy.The stereodynamics of the F+H_(2)(v=1,j=1)reaction is also analyzed theoretically,showing that minor differences exist for the reactants initially prepared in different spatial alignments.
基金supported by the National Natural Science Foundation of China(No.22203095,No.22103087,and No.22288201)the State Key Laboratory of Molecular Reaction Dynamics(SKLMRDZ202406)the Chinese Academy of Sciences(GJJSTD20220001).
文摘3-Furfural(C_(5)H_(4)O_(2))is a furan(C_(4)H_(4)O)derivative compound formed by replacing the hydrogen(H)atom at the ring 3-position with the aldehyde(CHO)group substituent.In this work,we intend to investigate the ultrafast decay dynamics of electronically excited 3-furfural using the femtosecond time-resolved photoelectron imaging technique.At pump wavelengths of 259.5,238.6 and 218.311m,two alternative decay mechanisms for the S_(2)(^(1)ππ*)state are tentatively proposed and discussed.Specifically,we prefer to suggest that a fraction of the initially prepared wavepacket in the S_(2)(^(1)ππ*)state is likely to undergo the subpicosecond relaxation via the S_(1)(^(1)nπ*)state.Presumably the lower lying T_(2)(^(3)ππ*)state is subsequently populated on a∼4 ps timescale via intersystem crossing from the minimum of the S_(1)(^(1)nπ*)state surface.The relaxation of the T_(2)(^(3)ππ*)state is sensitive to its vibrational excess energy and the value of its lifetime is 1.6±0.2 ns,280±30 ps and 50±10 ps for pump wavelengths of 259.5,238.6 and 218.3 m,respectively.
基金supported by the National Natural Science Foundation of China(No.22125302 and No.22327801)the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)the University of Science and Technology of China.
文摘Time-sliced velocity map ion imaging(VMI)experiments were performed to investigate the photodissociation of H_(2)S^(+)X^(2)B_(1),via the excitation to the A^(2)A_(1)(0,11,0)state.Experimental images of the S^(+)(^(4)Su)products were recorded near 349.60 nm for the K=1 band,and near 344.30 nm for the K=2 band.The derived product total kinetic energy release(TKER)spectra exhibit partially rotationally resolved structures corresponding to the H_(2)(X^(1)∑_(g)^(+))co-products.The observed product state and angular distributions both exhibit sensitive dependence on the photolysis wavelength at near 349.60 nm and 344.30 nm.These phenomena indicate the underlying rich dynamic details and the role of the rotational excitation of H_(2)S^(+).
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supported by the National Natural Science Foundation of China(No.21822305,No.21688102,No.22003067)the Chinese Academy of Sciences(No.XDB17000000)。
文摘The prototypical reaction of F+HD→DF+H was investigated at collision energies from 3.03 meV to 17.97 meV using a crossed molecular beam apparatus with multichannel Rydberg tagging time-of-flight detection.Significant contributions from both the BornOppenheimer(BO)forbidden reaction F^(*)(^(2)P_(1/2))+HD→DF+H and the BO-allowed reaction F(^(2)P_(3/2))+HD→DF+H were observed.In the backward scattering direction,the contribution from the BO-forbidden reaction F^(*)(^(2)P_(1/2))+HD was found to be considerably greater than the BO-allowed reaction F(^(2)P_(3/2))+HD,indicating the non-adiabatic effects play an important role in the dynamics of the title reaction at low collision energies.Collision-energy dependence of differential cross sections(DCSs)in the backward scattering direction was found to be monotonously decreased as the collision energy decreases,which does not support the existence of resonance states in this energy range.DCSs of both BO-allowed and BO-forbidden reactions were measured at seven collision energies from 3.03 meV to 17.97 meV.It is quite unexpected that the angular distribution gradually shifts from backward to sideway as the collision energy decreases from 17.97 meV to 3.03 meV,suggesting some unknown mechanisms may exist at low collision energies.
