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
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
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 dynamics of photostopping iodine atoms from electrically oriented ICI molecules was numerically studied based on their orientational probability distribution functions. Velocity distributions of the iodine atoms a...The dynamics of photostopping iodine atoms from electrically oriented ICI molecules was numerically studied based on their orientational probability distribution functions. Velocity distributions of the iodine atoms and their production rates were investigated for orienting electrical fields of various intensities. For the IC1 precursor beams with an initial rotational temperature of ~ 1 K, the production of the iodine atoms near zero speed will be improved by about ~ 5 times when an orienting electrical field of ~ 200 kV/cm is present. A production rate of ~ 0.5%0 is obtained for photostopped iodine atoms with speeds less than 10 m/s, which are suitable for magnetic trapping. The electrical orientation of IC1 precursors and magnetic trapping of photostopped iodine atoms in situ can be conveniently realized with a pair of charged ring magnets. With the maximal value of the trapping field being ~ 0.28 T, the largest trapping speed is ~ 7.0 m/s for the iodine atom.展开更多
We experimentally demonstrate the Coulomb explosion process of CS_2 molecule under a near-infrared（800 nm）intense femtosecond laser field by a DC-sliced ion imaging technique. We obtain the DC-sliced images of these...We experimentally demonstrate the Coulomb explosion process of CS_2 molecule under a near-infrared（800 nm）intense femtosecond laser field by a DC-sliced ion imaging technique. We obtain the DC-sliced images of these fragment ions S~＋, S^（2＋）, CS~＋, and CS^（2＋）by breaking one C–S bond, and assign their Coulomb explosion channels by considering their kinetic energy release and angular distribution. We also numerically simulate the dissociation dynamics of parent ions CS_2^（k＋）（k = 2–4） by a Coulomb potential approximation, and obtain the time evolution of Coulomb energy and kinetic energy release, which indicates that the dissociation time of parent ions CS_2^（k＋） decreases with the increase of the charge number k.These experimental and theoretical results can serve as a useful benchmark for those researchers who work in the related area.展开更多
In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH （A2△） molecules through using the multi-photon dissociation of ...In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH （A2△） molecules through using the multi-photon dissociation of （CH3）eCO, CH3NO2, CHzBr2, and CHBr3 at ~ 213 nm. The CH product intensity is measured by using the emission spectrum of CH （A2△→XeH）. The dependence of fluorescence intensity on laser power is studied, and the probable dissociation channels are analyzed. The relationship between the fluorescence intensity and some parameters, such as the temperature of the beam source, stagnation pressure, and the time delay between the opening of pulse valve and the photolysis laser, are also studied. The influence of three different carrier gases on CH signal intensity is investigated. The vibrational and rotational temperatures of the CH （Ae△） product are obtained by comparing experimental data with the simulated ones from the LIFBASE program.展开更多
The direct Coulomb explosion of N2O2+has been investigated experimentally after double-ionization by a single extreme ultraviolet(EUV)photon with an energy of ~38.5 eV.From the ion–ion time-of-flight coincidence spec...The direct Coulomb explosion of N2O2+has been investigated experimentally after double-ionization by a single extreme ultraviolet(EUV)photon with an energy of ~38.5 eV.From the ion–ion time-of-flight coincidence spectrum,the de-nitrogenation(N2O2+→N++NO+)and de-oxygenation(N2O2+→O++N+2)photodissociation channels of N2O2+are unequivocally identified.The measured kinetic energy release(KER)distribution of the de-nitrogenation channel presents a major peak accompanied by a shoulder structure.We find that the major peak can be attributed to the direct photodissociation of the 11△and 1^1Σ+states,while the shoulder structure should be ascribed to the predissociation of the1^1△and 1^1Σ+states via 13Πstate.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.
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supported by the National Natural Science Foundation of China(Grant Nos.11034002,61205198,and 11274114)the National Key Basic Research and Development Program of China(Grant No.2011CB921602)
文摘The dynamics of photostopping iodine atoms from electrically oriented ICI molecules was numerically studied based on their orientational probability distribution functions. Velocity distributions of the iodine atoms and their production rates were investigated for orienting electrical fields of various intensities. For the IC1 precursor beams with an initial rotational temperature of ~ 1 K, the production of the iodine atoms near zero speed will be improved by about ~ 5 times when an orienting electrical field of ~ 200 kV/cm is present. A production rate of ~ 0.5%0 is obtained for photostopped iodine atoms with speeds less than 10 m/s, which are suitable for magnetic trapping. The electrical orientation of IC1 precursors and magnetic trapping of photostopped iodine atoms in situ can be conveniently realized with a pair of charged ring magnets. With the maximal value of the trapping field being ~ 0.28 T, the largest trapping speed is ~ 7.0 m/s for the iodine atom.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51132004 and 11474096)the Science and Technology Commission of Shanghai Municipality,China(Grant No.14JC1401500)the support of the NYU-ECNU Institute of Physics at NYU Shanghai,China
文摘We experimentally demonstrate the Coulomb explosion process of CS_2 molecule under a near-infrared（800 nm）intense femtosecond laser field by a DC-sliced ion imaging technique. We obtain the DC-sliced images of these fragment ions S~＋, S^（2＋）, CS~＋, and CS^（2＋）by breaking one C–S bond, and assign their Coulomb explosion channels by considering their kinetic energy release and angular distribution. We also numerically simulate the dissociation dynamics of parent ions CS_2^（k＋）（k = 2–4） by a Coulomb potential approximation, and obtain the time evolution of Coulomb energy and kinetic energy release, which indicates that the dissociation time of parent ions CS_2^（k＋） decreases with the increase of the charge number k.These experimental and theoretical results can serve as a useful benchmark for those researchers who work in the related area.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10674047,10804031,10904037,10904060,10974055,11034002,11274114,and 61205198)the National Key Basic Research and Development Program of China(Grant Nos.2006CB921604 and 2011CB921602)+2 种基金the Basic Key Program of Shanghai Municipality,China(Grant No.07JC14017)the Fundamental Research Funds for the Central Universitiesthe Shanghai Leading Academic Discipline Project,China(Grant No.B408)
文摘In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH （A2△） molecules through using the multi-photon dissociation of （CH3）eCO, CH3NO2, CHzBr2, and CHBr3 at ~ 213 nm. The CH product intensity is measured by using the emission spectrum of CH （A2△→XeH）. The dependence of fluorescence intensity on laser power is studied, and the probable dissociation channels are analyzed. The relationship between the fluorescence intensity and some parameters, such as the temperature of the beam source, stagnation pressure, and the time delay between the opening of pulse valve and the photolysis laser, are also studied. The influence of three different carrier gases on CH signal intensity is investigated. The vibrational and rotational temperatures of the CH （Ae△） product are obtained by comparing experimental data with the simulated ones from the LIFBASE program.
基金National Key Research and Development Program of China(Grant No.2017YFA0402300).
文摘The direct Coulomb explosion of N2O2+has been investigated experimentally after double-ionization by a single extreme ultraviolet(EUV)photon with an energy of ~38.5 eV.From the ion–ion time-of-flight coincidence spectrum,the de-nitrogenation(N2O2+→N++NO+)and de-oxygenation(N2O2+→O++N+2)photodissociation channels of N2O2+are unequivocally identified.The measured kinetic energy release(KER)distribution of the de-nitrogenation channel presents a major peak accompanied by a shoulder structure.We find that the major peak can be attributed to the direct photodissociation of the 11△and 1^1Σ+states,while the shoulder structure should be ascribed to the predissociation of the1^1△and 1^1Σ+states via 13Πstate.
