Fewest-switches surfacing hopping(FSSH) simulations have been performed with the high-level multi-reference electronic structure method to explore the coupled electronic and nuclear dynamics upon photoexcitation of cy...Fewest-switches surfacing hopping(FSSH) simulations have been performed with the high-level multi-reference electronic structure method to explore the coupled electronic and nuclear dynamics upon photoexcitation of cyanogen bromide(BrCN). The potential energy surfaces(PES) of BrCN are charted as functions of the Jacobi coordinates(R, θ). An indepth examination of the FSSH trajectories reveals the temporal dynamics of the molecule and the population changes of the lowest twelve states during BrCN's photodissociation process, which presents a rich tapestry of dynamical information.Furthermore, the carbon K-edge x-ray absorption spectroscopy(XAS) is calculated with multi-reference inner-shell spectral simulations. The rotation of the CN fragment and the elongation of the C–Br bond are found to be the reason for the peak shifting in the XAS. Our findings offer a nuanced interpretation for inner-shell probe investigations of BrCN, setting the stage for a deeper understanding of the photodissociation process of cyanogen halides molecules.展开更多
A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ...A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ion yield is observed. More than ten-fold changes of ion yield ratio between different products can be realized. The experimental observations further explain the compositions and formation pathways of peaks in the mass spectra. The controlling mechanisms are also discussed.展开更多
Photodissociation of oxygen from oxymyoglobin(oxyMb) was investigated by means of fluorescence spectroscopy. One of the most important findings of the photodissociation of oxyMb was the discovery of two processes wh...Photodissociation of oxygen from oxymyoglobin(oxyMb) was investigated by means of fluorescence spectroscopy. One of the most important findings of the photodissociation of oxyMb was the discovery of two processes which were affected by excitation intensity, temperature, solvent viscosity, and excitation wavelength. Process I(PI) corresponded to oxygen escaping from the binding site at ferrous heme iron atom within the porphyrin ring into the heme pocket, whereas process II(PII) was ascribed to oxygen escaping from the heme pocket into the solvent. To elucidate this interesting phenomenon, we proposed a model that oxygen encountered two barriers on its way from the binding site at the ferrous heme iron to the solvent. Reversibility and wavelength sensitivity of the photodissociation were also observed.展开更多
The ultrafast photodissociation dynamics of thionyl chloride after excitation with a 235 nm pump pulse has been studied using a femtosecond time-resolved mass spectroscopy.The observed parent transient suggests that t...The ultrafast photodissociation dynamics of thionyl chloride after excitation with a 235 nm pump pulse has been studied using a femtosecond time-resolved mass spectroscopy.The observed parent transient suggests that the excited states initiated by 235 nm are very shortlived,that is,approximately 166 fs.Not only a stepwise three-body dissociation pathway but also a concerted three-body dissociation pathway is observed.展开更多
The photoabsorption and photodissociation of carbon monoxide(CO)in the vacuum ultraviolet(VUV)region is one of the most important photochemical processes in the interstellar medium,thus it has attracted numerous exper...The photoabsorption and photodissociation of carbon monoxide(CO)in the vacuum ultraviolet(VUV)region is one of the most important photochemical processes in the interstellar medium,thus it has attracted numerous experimental and theoretical studies.Here,we employed the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging method to measure the relative branching ratios[C(3P0)+O(1D)]/{[C(3P0)+O(3P)]+[C(3P0)+O(1D)]}and[C(3P2)+O(1D)]/{[C(3P2)+O(3P)]+[C(3P2)+O(1D)]}in the VUV photoexcitation energy range of 108000-113200 cm^−1.Here,one tunable VUV laser beam is used to excite CO to speci c rovibronic states,and a second independently tunable VUV laser beam is used to state-selectively ionize C(3P0)and C(3P2)for detection.State-selective photoionization through the 1VUV+1UV/visible resonance-enhanced multiphoton ionization scheme has greatly enhanced the detection sensitivity,which makes many new weak absorption bands observable in the current study.The branching ratio measurement shows that the spin-forbidden channels C(3P0)+O(1D)and C(3P2)+O(1D)only open at several discrete narrow energy windows.This might be caused by certain accidental resonanceenhanced spin-orbit interactions between the directly excited Rydberg states and valence states of triplet type which nally dissociate into the spin-forbidden channels.展开更多
This paper performs multi-reference second-order perturbation theory calculations on the ground state and a number of low-lying excited states of HSCH3 molecule, and calculates the vertical excitation energies and low...This paper performs multi-reference second-order perturbation theory calculations on the ground state and a number of low-lying excited states of HSCH3 molecule, and calculates the vertical excitation energies and low-energy potential-energy curves, based on which the photodissociation channels of HSCH3 at 193,222,248 nm are clarified.展开更多
Photodissociation of CH_aI dimer at 248nm is studied on a rotatable crossed laser—molecular beam apparatus,About 93% of the available energy goes into the internal excitation,wlich is much higher than in the case of ...Photodissociation of CH_aI dimer at 248nm is studied on a rotatable crossed laser—molecular beam apparatus,About 93% of the available energy goes into the internal excitation,wlich is much higher than in the case of CH_3I monomer.展开更多
Wave packet propagation techniques are used to find experimentally reliable laser parameters that yield optimal production. The photoionization and photodissoeiation dynamics of sodium iodine molecules are interpreted...Wave packet propagation techniques are used to find experimentally reliable laser parameters that yield optimal production. The photoionization and photodissoeiation dynamics of sodium iodine molecules are interpreted into several channels. Several frequencies are found to be suitable for Nal molecules during the photoionization and dissociation processes. Photon-dressed excited states and electron-dressed ionic continuum states facilitate the search for available laser parameters.展开更多
An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed la...An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed laser vaporization supersonic ion source are skimmed and mass separated by a Wiley-McLaren time-of-flight mass spectrometer.The ion of interest is mass selected,decelerated and dissociated by a tunable IR laser.The fragment and parent ions are reaccelerated and mass analyzed by the second time-of-flight mass spectrometer.A simple new assembly integrated with mass gate,deceleration and reacceleration ion optics was designed,which allows us to measure the infrared spectra of mass selected ions with high sensitivity and easy timing synchronization.展开更多
The photodissociation of ethyl iodide at 279.71, 281.73, 304.02 and 304.67 nm has been studied on our new mini-photofragment translational spectrometer with a total flight path of only 5 cm. Some vibra-tional peaks ar...The photodissociation of ethyl iodide at 279.71, 281.73, 304.02 and 304.67 nm has been studied on our new mini-photofragment translational spectrometer with a total flight path of only 5 cm. Some vibra-tional peaks are firstly resolved in the TOF spectra of I*(2P1/2) and I(2P3/2) channels. These vibrational peaks are assigned to the excitation states (ν2 = 0, 1, 2,…) of the umbrella mode (ν2, 540 cm-1) of the photofragment C2H5, and the distribution of the vibrational states is obtained. The dissociation energy has been determined to be D0(C-I)=2.314 ± 0.03 eV. The energy partitioning of the available energy (Eavl=ET+Eint=ET+EV,R) calculated from our experimental data E int /E avl= 22.1% at 281.73 nm, 22.4% at 304.02 nm for the I* channel, and E int /E avl= 25.2% at 279.71 nm, 25.9% at 304.67 nm for the I channel, seem to be more reliable.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
Based on the ab initio calculation results, the hydrogen atom transfer has been investigated. In order to explain the experimental results, a new mechanism is proposed, that is, hydrogen transfer occurs before but not...Based on the ab initio calculation results, the hydrogen atom transfer has been investigated. In order to explain the experimental results, a new mechanism is proposed, that is, hydrogen transfer occurs before but not after Cl atom eliminates from aromatic ring. The calculation result strongly supports this mechanism.展开更多
This paper presents a general formula for the angular distribution in the direct photo-dissociation of polyatomic molecules, in which the asymmetry of the parent and fragmentmolecules, the polarization of the radiatio...This paper presents a general formula for the angular distribution in the direct photo-dissociation of polyatomic molecules, in which the asymmetry of the parent and fragmentmolecules, the polarization of the radiation field, the number of photons absorbed, the tran-sition dipole moment orientation, and the recoil direction have been explicitly considered.展开更多
The photodissociation mechanism of benzyl chloride (BzCl) under 248 nm has been investigated by the complete active space SCF (CASSCF) method by calculating the geometries of the ground (S0) and lower excited st...The photodissociation mechanism of benzyl chloride (BzCl) under 248 nm has been investigated by the complete active space SCF (CASSCF) method by calculating the geometries of the ground (S0) and lower excited states, the vertical (Tv) and adiabatic (T0) excitation energies of the lower states, and the dissociation reaction pathways on the potential energy surfaces (PES) of SI, TI and T2 states. The calculated results clearly elucidated the photodissociation mechanism of BzCl, and indicated that the photodissociation on the PES of T1 state is the most favorable.展开更多
The wave packet dynamics of I2^- anions is studied by using the time-dependent wave packet method. Two conclusions can be drawn from the calculations. First, the period of the total photoelectron signal oscillating wi...The wave packet dynamics of I2^- anions is studied by using the time-dependent wave packet method. Two conclusions can be drawn from the calculations. First, the period of the total photoelectron signal oscillating with the propagation of delay time is about 750fs. Second, the photoionization of I2^- anions begin at the time 600 fs, and the time needed for the population of the electronic state of I2 neutral molecule to reach the maximum becomes shorter with the increasing delay time.展开更多
The state selection and beam focus of linear triatomic molecules (OCS, HCN, ClCN, BrCN and ICN) with doubling states in a hexapole electric field have been numerically realized. The method is based on a quantum mech...The state selection and beam focus of linear triatomic molecules (OCS, HCN, ClCN, BrCN and ICN) with doubling states in a hexapole electric field have been numerically realized. The method is based on a quantum mechanical treatment of the molecular Stark energy and a classical mechanical treatment for the molecular trajectory in the field. In linear molecules with doubling states, the second-order Stark effect can be neglected and the doubling states have the same value of J and M. The influences of the molecular properties, state energies, and the apparatus parameters such as molecular beam temperature and length of the hexapole, on the role of state selection and focus have been discussed. The method established here can be taken as a guide for hexapole experiment of orientation of polar molecules.展开更多
The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoreticaly studied by using the time-dependent quantum wave packet method. Both the internuclear distan...The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoreticaly studied by using the time-dependent quantum wave packet method. Both the internuclear distance-and velocity-dependent density functions are calculated and discussed. It is demonstrated that the interference pattern is determined by the phase difference and the delay time between two pump pulses. With two identical pulses with a delay time of 305 fs and a FWHM of 20 fs, more interference fringes can be observed, while with two pump pulses with a delay time of 80 fs and a FWHM of 20 fs, only a few interference fringes can be observed.展开更多
An ab initio investigation of electronic curve crossing in a methyl iodide molecule is carried out using spin-orbit multiconfigurational quasidegenerate perturbation theory. The one-dimensional rigid potential curves ...An ab initio investigation of electronic curve crossing in a methyl iodide molecule is carried out using spin-orbit multiconfigurational quasidegenerate perturbation theory. The one-dimensional rigid potential curves and optimized effective curves of low-lying states, including spin-orbit coupling and relativistic effects, are calculated. The spin-orbit electronic curve crossing between ^3Qo+ and ^1Q1, and the shadow minimum in potential energy curve of ^3Qo+ at large internuclear distance are found in both sets of the curves according to the present calcu- lations. The crossing position is in the range of Re-1 = 0.2370 3:0.0001 nm. Comparisons with other reports are presented.展开更多
Effect of laser fields on Na2 interaction potentials is studied by calculating the time-resolved photoelectron spectrum (TRPES) with the time-dependent wave-packet method. It is shown that the photoelectron spectrum...Effect of laser fields on Na2 interaction potentials is studied by calculating the time-resolved photoelectron spectrum (TRPES) with the time-dependent wave-packet method. It is shown that the photoelectron spectrum at different delay times reflects the population in different electronic states. We inspect the periodicity of vibrational motion in neutral states, and map the vibrational wave-packet propagation in corresponding internuclear coordinate.展开更多
The [1+1] two-photon dissociation dynamics of mass-selected 79Br2 + has been studied in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The quartet 14Σ- u;3=2 state of 79Br2 ...The [1+1] two-photon dissociation dynamics of mass-selected 79Br2 + has been studied in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The quartet 14Σ- u;3=2 state of 79Br2 + is employed as an intermediate state to initiate resonance enhanced two-photon excitation to high-lying dissociative states in the 4.0-5.0 eV energy region above the ground rovibronic state. Total kinetic energy release (TKER) and the twodimensional recoiling velocity distributions of fragmented 79Br+ ions are measured using the technique of DC-slice velocity map imaging. Branching ratios for individual state-resolved product channels are determined from the TKER spectra. The measured photofragment angular distributions indicate that the dissociation of 79Br2 + occurs in dissociative Ω=3/2 state via ΔΩ=0 parallel transition from the 14Σ-u;3=2 intermediate state. Due to the considerable spin-orbit coupling effects in the excited states of 79Br2 +, higher-lying dissociative quartet states are likely responsible for the observed photodissociation processes.展开更多
基金supported by the start-up funding of ShanghaiTech University in Chinasupported by a user project at the Molecular Foundry (LBNL) and its computing resources administered by the High-Performance Computing Services Group at LBNL+2 种基金supported by the Office of Science and Office of Basic Energy Sciences of the U.S.Department of Energy (Grant No.DE-AC02-05CH11231)the National Energy Research Scientific Computing Center (NERSC),a U.S.Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory (Grant No.DE-AC02-05CH11231)supported by the High-Performance Computing (HPC) Platform of ShanghaiTech University。
文摘Fewest-switches surfacing hopping(FSSH) simulations have been performed with the high-level multi-reference electronic structure method to explore the coupled electronic and nuclear dynamics upon photoexcitation of cyanogen bromide(BrCN). The potential energy surfaces(PES) of BrCN are charted as functions of the Jacobi coordinates(R, θ). An indepth examination of the FSSH trajectories reveals the temporal dynamics of the molecule and the population changes of the lowest twelve states during BrCN's photodissociation process, which presents a rich tapestry of dynamical information.Furthermore, the carbon K-edge x-ray absorption spectroscopy(XAS) is calculated with multi-reference inner-shell spectral simulations. The rotation of the CN fragment and the elongation of the C–Br bond are found to be the reason for the peak shifting in the XAS. Our findings offer a nuanced interpretation for inner-shell probe investigations of BrCN, setting the stage for a deeper understanding of the photodissociation process of cyanogen halides molecules.
基金Project supported by the National Basic Research Program of China (973 Program) (Grant No.2013CB922200)the National Natural Science Foundation of China,(Grant Nos.10774056 and 10974070)+1 种基金the Fundamental Research Funds for the Central Universities,China (Grant No.200903371)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No.20100061110045)
文摘A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ion yield is observed. More than ten-fold changes of ion yield ratio between different products can be realized. The experimental observations further explain the compositions and formation pathways of peaks in the mass spectra. The controlling mechanisms are also discussed.
基金Supported by the National Natural Science Foundation of China(No.20871024)the Program for Liaoning Excellent Talents in University,China(No.RC-04-10)+1 种基金the Fund of Liaoning Innovative Research Team in University,China(Nos.2006T002,2008T005,2009T003)the Plan Project of Dalian Science and Technology,China(No.2008E11SF170)
文摘Photodissociation of oxygen from oxymyoglobin(oxyMb) was investigated by means of fluorescence spectroscopy. One of the most important findings of the photodissociation of oxyMb was the discovery of two processes which were affected by excitation intensity, temperature, solvent viscosity, and excitation wavelength. Process I(PI) corresponded to oxygen escaping from the binding site at ferrous heme iron atom within the porphyrin ring into the heme pocket, whereas process II(PII) was ascribed to oxygen escaping from the heme pocket into the solvent. To elucidate this interesting phenomenon, we proposed a model that oxygen encountered two barriers on its way from the binding site at the ferrous heme iron to the solvent. Reversibility and wavelength sensitivity of the photodissociation were also observed.
基金This work was supported by the National Natural Science Foundation of China(No.11564040,No.21763027,No.11204264,No.11464045),the Natural Science Foundation of Xinjiang(No.2017D01B36),“13th Five-Year”Plan for Key Discipline Physics Bidding Project(No.17SDKD0602),Xinjiang Normal University and Science Foundation for Doctorate Research of Xinjiang Normal University(XJNUBS1511,XJNUBS1408),Teaching research and reform program of Xinjiang Normal University(No:SDJG2016C8).
文摘The ultrafast photodissociation dynamics of thionyl chloride after excitation with a 235 nm pump pulse has been studied using a femtosecond time-resolved mass spectroscopy.The observed parent transient suggests that the excited states initiated by 235 nm are very shortlived,that is,approximately 166 fs.Not only a stepwise three-body dissociation pathway but also a concerted three-body dissociation pathway is observed.
基金the National Natural Science Foundation of China(No.21803072)the Program for Young Outstanding Scientists of Institute of Chemistry,Chinese Academy of Science(ICCAS),and Beijing National Laboratory for Molecular Sciences(BNLMS).+1 种基金the National Aeronautics and Space Administration Award #80NSSC18K0592 and National Science Foundation under CHE-1763319.Yu SongWilliam.M.Jackson gratefully acknowledge the support of NSF under grants CHE-1301501 and AST-1410297.
文摘The photoabsorption and photodissociation of carbon monoxide(CO)in the vacuum ultraviolet(VUV)region is one of the most important photochemical processes in the interstellar medium,thus it has attracted numerous experimental and theoretical studies.Here,we employed the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging method to measure the relative branching ratios[C(3P0)+O(1D)]/{[C(3P0)+O(3P)]+[C(3P0)+O(1D)]}and[C(3P2)+O(1D)]/{[C(3P2)+O(3P)]+[C(3P2)+O(1D)]}in the VUV photoexcitation energy range of 108000-113200 cm^−1.Here,one tunable VUV laser beam is used to excite CO to speci c rovibronic states,and a second independently tunable VUV laser beam is used to state-selectively ionize C(3P0)and C(3P2)for detection.State-selective photoionization through the 1VUV+1UV/visible resonance-enhanced multiphoton ionization scheme has greatly enhanced the detection sensitivity,which makes many new weak absorption bands observable in the current study.The branching ratio measurement shows that the spin-forbidden channels C(3P0)+O(1D)and C(3P2)+O(1D)only open at several discrete narrow energy windows.This might be caused by certain accidental resonanceenhanced spin-orbit interactions between the directly excited Rydberg states and valence states of triplet type which nally dissociate into the spin-forbidden channels.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10604022 and 60278009)
文摘This paper performs multi-reference second-order perturbation theory calculations on the ground state and a number of low-lying excited states of HSCH3 molecule, and calculates the vertical excitation energies and low-energy potential-energy curves, based on which the photodissociation channels of HSCH3 at 193,222,248 nm are clarified.
文摘Photodissociation of CH_aI dimer at 248nm is studied on a rotatable crossed laser—molecular beam apparatus,About 93% of the available energy goes into the internal excitation,wlich is much higher than in the case of CH_3I monomer.
基金supported by the Natural Science Foundation Project of the Shandong Province(No.ZR2011AM010)the University Science and Technology Planning Program of Shandong Province(No.J10LB60)
文摘Wave packet propagation techniques are used to find experimentally reliable laser parameters that yield optimal production. The photoionization and photodissoeiation dynamics of sodium iodine molecules are interpreted into several channels. Several frequencies are found to be suitable for Nal molecules during the photoionization and dissociation processes. Photon-dressed excited states and electron-dressed ionic continuum states facilitate the search for available laser parameters.
基金supported by the Ministry of Science and Technology of China(2013CB834603,2012YQ220113-3,and 2011YQ06010003)the National Natural Science Foundation of China(21273045 and 20933030)the Committee of Science and Technology of Shanghai(13XD1400800)
文摘An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed laser vaporization supersonic ion source are skimmed and mass separated by a Wiley-McLaren time-of-flight mass spectrometer.The ion of interest is mass selected,decelerated and dissociated by a tunable IR laser.The fragment and parent ions are reaccelerated and mass analyzed by the second time-of-flight mass spectrometer.A simple new assembly integrated with mass gate,deceleration and reacceleration ion optics was designed,which allows us to measure the infrared spectra of mass selected ions with high sensitivity and easy timing synchronization.
基金Supported by the National Natural Science Foundation of China (Grant No. 20433080)
文摘The photodissociation of ethyl iodide at 279.71, 281.73, 304.02 and 304.67 nm has been studied on our new mini-photofragment translational spectrometer with a total flight path of only 5 cm. Some vibra-tional peaks are firstly resolved in the TOF spectra of I*(2P1/2) and I(2P3/2) channels. These vibrational peaks are assigned to the excitation states (ν2 = 0, 1, 2,…) of the umbrella mode (ν2, 540 cm-1) of the photofragment C2H5, and the distribution of the vibrational states is obtained. The dissociation energy has been determined to be D0(C-I)=2.314 ± 0.03 eV. The energy partitioning of the available energy (Eavl=ET+Eint=ET+EV,R) calculated from our experimental data E int /E avl= 22.1% at 281.73 nm, 22.4% at 304.02 nm for the I* channel, and E int /E avl= 25.2% at 279.71 nm, 25.9% at 304.67 nm for the I channel, seem to be more reliable.
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.
文摘Based on the ab initio calculation results, the hydrogen atom transfer has been investigated. In order to explain the experimental results, a new mechanism is proposed, that is, hydrogen transfer occurs before but not after Cl atom eliminates from aromatic ring. The calculation result strongly supports this mechanism.
基金Project supported by a grant from the National Committee of Science and Technology
文摘This paper presents a general formula for the angular distribution in the direct photo-dissociation of polyatomic molecules, in which the asymmetry of the parent and fragmentmolecules, the polarization of the radiation field, the number of photons absorbed, the tran-sition dipole moment orientation, and the recoil direction have been explicitly considered.
基金Project supported by the National Natural Science Foundation of China (Nos. 20472011, 20673012) and the Major State Basic Research Development Programs (Nos. 2004CB719903, 2002CB613406).
文摘The photodissociation mechanism of benzyl chloride (BzCl) under 248 nm has been investigated by the complete active space SCF (CASSCF) method by calculating the geometries of the ground (S0) and lower excited states, the vertical (Tv) and adiabatic (T0) excitation energies of the lower states, and the dissociation reaction pathways on the potential energy surfaces (PES) of SI, TI and T2 states. The calculated results clearly elucidated the photodissociation mechanism of BzCl, and indicated that the photodissociation on the PES of T1 state is the most favorable.
基金Supported by the National Natural Science Foundation of China under Grant No 10575017. The code used in our calculation is provided by Professor Ke-Li Han and we appreciate his help and kind advice.
文摘The wave packet dynamics of I2^- anions is studied by using the time-dependent wave packet method. Two conclusions can be drawn from the calculations. First, the period of the total photoelectron signal oscillating with the propagation of delay time is about 750fs. Second, the photoionization of I2^- anions begin at the time 600 fs, and the time needed for the population of the electronic state of I2 neutral molecule to reach the maximum becomes shorter with the increasing delay time.
基金Supported by the National Natural Science Foundation of China and the Specialized Research Fund for the Doctoral Programme of Higher Education of China.
文摘The state selection and beam focus of linear triatomic molecules (OCS, HCN, ClCN, BrCN and ICN) with doubling states in a hexapole electric field have been numerically realized. The method is based on a quantum mechanical treatment of the molecular Stark energy and a classical mechanical treatment for the molecular trajectory in the field. In linear molecules with doubling states, the second-order Stark effect can be neglected and the doubling states have the same value of J and M. The influences of the molecular properties, state energies, and the apparatus parameters such as molecular beam temperature and length of the hexapole, on the role of state selection and focus have been discussed. The method established here can be taken as a guide for hexapole experiment of orientation of polar molecules.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10674022 and 20633070)
文摘The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoreticaly studied by using the time-dependent quantum wave packet method. Both the internuclear distance-and velocity-dependent density functions are calculated and discussed. It is demonstrated that the interference pattern is determined by the phase difference and the delay time between two pump pulses. With two identical pulses with a delay time of 305 fs and a FWHM of 20 fs, more interference fringes can be observed, while with two pump pulses with a delay time of 80 fs and a FWHM of 20 fs, only a few interference fringes can be observed.
文摘An ab initio investigation of electronic curve crossing in a methyl iodide molecule is carried out using spin-orbit multiconfigurational quasidegenerate perturbation theory. The one-dimensional rigid potential curves and optimized effective curves of low-lying states, including spin-orbit coupling and relativistic effects, are calculated. The spin-orbit electronic curve crossing between ^3Qo+ and ^1Q1, and the shadow minimum in potential energy curve of ^3Qo+ at large internuclear distance are found in both sets of the curves according to the present calcu- lations. The crossing position is in the range of Re-1 = 0.2370 3:0.0001 nm. Comparisons with other reports are presented.
基金Supported by the National Natural Science Foundation of China under Grant No 10575017.
文摘Effect of laser fields on Na2 interaction potentials is studied by calculating the time-resolved photoelectron spectrum (TRPES) with the time-dependent wave-packet method. It is shown that the photoelectron spectrum at different delay times reflects the population in different electronic states. We inspect the periodicity of vibrational motion in neutral states, and map the vibrational wave-packet propagation in corresponding internuclear coordinate.
基金the National Natural Science Foundation of China(No.21773221 and No.21827804),the National Key R&D Program of China(2017YFA0303502),and Fundamental Research Funds for the Central Universities of China(WK2340000078).
文摘The [1+1] two-photon dissociation dynamics of mass-selected 79Br2 + has been studied in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The quartet 14Σ- u;3=2 state of 79Br2 + is employed as an intermediate state to initiate resonance enhanced two-photon excitation to high-lying dissociative states in the 4.0-5.0 eV energy region above the ground rovibronic state. Total kinetic energy release (TKER) and the twodimensional recoiling velocity distributions of fragmented 79Br+ ions are measured using the technique of DC-slice velocity map imaging. Branching ratios for individual state-resolved product channels are determined from the TKER spectra. The measured photofragment angular distributions indicate that the dissociation of 79Br2 + occurs in dissociative Ω=3/2 state via ΔΩ=0 parallel transition from the 14Σ-u;3=2 intermediate state. Due to the considerable spin-orbit coupling effects in the excited states of 79Br2 +, higher-lying dissociative quartet states are likely responsible for the observed photodissociation processes.