We propose an efficient method for the generation of an isolated attosecond pulse from the asymmetric molecular ions HeH^2+ by adding a half-cycle-like field (HCLF) to the fundamental driving laser field. The high-...We propose an efficient method for the generation of an isolated attosecond pulse from the asymmetric molecular ions HeH^2+ by adding a half-cycle-like field (HCLF) to the fundamental driving laser field. The high-order harmonic generation (HHG) is investigated by numerically sowing the time-dependent Schrodinger equation. By performing the time-frequency distributions and the electronic wave packet probability densities, we find that the optimizing combined field is not only useful for extending the HHG cutoff, but also for simplifying the recombination channels through controlling the electron localization. In addition, by adjusting the intensity of the HCLF, a dominant short quantum path is selected to contribute the HHG spectrum. As a result, a 75-as isolated attosecond pulse is obtained by superposing a proper range of the harmonics.展开更多
In this paper, we overview recent advances in high-precision structure calculations of the hydrogen molecular ions (H2+ and HD+), including nonrelativistic energy eigenvalues and relativistic and quantum electrody...In this paper, we overview recent advances in high-precision structure calculations of the hydrogen molecular ions (H2+ and HD+), including nonrelativistic energy eigenvalues and relativistic and quantum electrodynamic corrections. In combination with high-precision measurements, it is feasible to precisely determine a molecular-based value of the proton- to-electron mass ratio. An experimental scheme is presented for measuring the rovibrational transition frequency (v,L) : (0, 0) → (6,1) in HD+, which is currently underway at the Wuhan Institute of Physics and Mathematics.展开更多
The high-order harmonic generation from an asymmetric molecular ion is theoretically investigated based on the Born-Oppenheimer model with two-dimensional electron dynamics.It is shown that the harmonic intensity chan...The high-order harmonic generation from an asymmetric molecular ion is theoretically investigated based on the Born-Oppenheimer model with two-dimensional electron dynamics.It is shown that the harmonic intensity changes periodically in elliptically polarized laser fields.The periodical character is ellipticity-dependent.By establishing the physical image,the periodicity of the harmonic intensity can be ascribed to the contributions of the ground state and the excited state.Furthermore,the electron dynamics from different electronic states can be selected via combining the elliptically polarized laser field with a static electric field.The harmonics dominated either by ground state or excited state are emitted once in an optical cycle in the combined laser field.展开更多
High-order harmonic generation from one-dimensional (1D) multi-atom molecular ions ill an ultra-short laser field is theoretically- investigated, The dynamics of the electron in a linearly polarized intense laser fi...High-order harmonic generation from one-dimensional (1D) multi-atom molecular ions ill an ultra-short laser field is theoretically- investigated, The dynamics of the electron in a linearly polarized intense laser field is analyzed in terms of 1D Schroedinger equation with the Crank-Nicolson algorithm, The dependence of high-order harmonics on the laser frequeney and the biter-nuclear distance is discussed, It is found that the optimum range of inter-nuclear distance should be changed to get extended harmonic generation for different laser frequency, and the lower frequency laser pulse is favorable to higher order harmonic generation as the inter-nuclear distance increases.展开更多
We theoretically investigate the electron localization around two nuclei in harmonic emission from asymmetric molecular ion. The results show that the ionization process of electron localized around one nucleus compet...We theoretically investigate the electron localization around two nuclei in harmonic emission from asymmetric molecular ion. The results show that the ionization process of electron localized around one nucleus competes with its transfer process to the other nucleus. By increasing the initial vibrational level, more electrons localized around the nucleus D+ tend to transfer to the nucleus He2+ so that the ionizations of electrons localized around the nucleus He2+ increase. In this case, the difference in harmonic efficiency between Hell2+ and HeD2+ decreases while the difference in harmonic spectral structure increases. The evident minimum can be observed the spectral structure of HeD2+, which is due to the strong in the harmonic spectrum of Hell2+ compared with that in interference of multiple recombination channels originating from two nuclei. Time-dependent nuclear probability density, electron-nuclear probability density, double-well model, and time-frequency maps are presented to explain the underlying mechanisms.展开更多
The photoelectron momentum distribution of H+ in circularly polarized laser fields is studied based on classical trajectory calculations. We screen Coulomb potentials at different radii, and trace trajectories of an ...The photoelectron momentum distribution of H+ in circularly polarized laser fields is studied based on classical trajectory calculations. We screen Coulomb potentials at different radii, and trace trajectories of an ensemble of electrons in such screened Coulomb potentials and circularly polarized laser fields. Simulations show that electron trajectories are bent by Coulomb fields, resulting in the laser-intensity-dependent drift of photoelectron momentum distributions in the laser polarization plane. This study intuitively explains how Coulomb potentials modify photoelectron momenta.展开更多
As an improvement on our previous work [J. Phys. B: At. Mol. Opt. Phys. 45 085101(2012)], an accurate method combining the spheroidal coordinates and B-spline basis is applied to study the ground state 1σg and low...As an improvement on our previous work [J. Phys. B: At. Mol. Opt. Phys. 45 085101(2012)], an accurate method combining the spheroidal coordinates and B-spline basis is applied to study the ground state 1σg and low excited states1σu, 1πg,u, 1δg,u, 2σg of the H+2in magnetic fields ranging from 10^9Gs(1 Gs = 10^-4T) to 4.414 × 10^13 Gs. Comparing the one-center method used in our previous work, the present method has a higher precision with a shorter computing time.Equilibrium distances of the states of the H+2in strong magnetic fields were found to be accurate to 3-5 significant digits(s.d.) and the total energies 6-11 s.d., even for some antibonding state, such as 1πg, which is difficult for the one-center method to give reliable results while the field strength is B ≥ 10^13 Gs. For the large disagreement in previous works, such as the equilibrium distances of the 1πg state at B = 10^9 Gs, the present data may be used as a reference. Further, the potential energy curves(PECs) and the electronic probability density distributions(EPDDs) of the bound states 1σg, 1πu, 1δg and antibonding states 1σu, 1πg, 1δu for B = 1, 10, 100, 1000 a.u.(atomic unit) are compared, so that the different influences of the magnetic fields on the chemical bonds of the bound states and antibonding states are discussed in detail.展开更多
The photodetachment of a hetero-nuclear diatomic molecular negative ion is studied by using a two-centre model. An analytic formula is presented for the electron flux distribution of a heteronuclear diatomic molecular...The photodetachment of a hetero-nuclear diatomic molecular negative ion is studied by using a two-centre model. An analytic formula is presented for the electron flux distribution of a heteronuclear diatomic molecular negative ion. Taking HF- as an example, we calculated the electron flux distributions of this ion for various detached electron energies. The results show that the electron flux distributions exhibit oscillatory structures, which are caused by the interference effect between the two nuclei. Besides, the laser light polarization also has a great influence on the electron flux distribution. The oscillation amplitude is the largest when the laser polarization is parallel to the z-axis; when the laser polarization is perpendicular to the z-axis, the oscillation almost vanishes. This study provides a new understanding of the photodetachment of a heteronuclear diatomic molecular negative ion.展开更多
Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can b...Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can be synthesized either naturally or artificially. To examine the metabolism and regulate the synthesis process, compounds labeled with nitrogen or carbon isotopes need to be used. These isotopic compounds allow for more extensive research and enable studies that would otherwise be impossible. However, their use is dependent on the availability of simple, efficient methods for isotopic analysis. Currently, the determination of the atomic fraction of carbon and nitrogen isotopes is only possible through their conversion into molecular nitrogen or carbon monoxide or carbon dioxide. This leads to the loss of information about isotopic enrichment in specific centers of the molecule. This article explores a new direct approach to determining the atomic fraction of carbon and nitrogen isotopes in the isotope-modified or identical centers of these compounds. This method eliminates the transfer process and dilution due to nitrogen and carbon impurities. It is now possible to simultaneously determine the atomic fraction of nitrogen and carbon isotopes in the research substance. This method can be applied to amino acids, making it an effective tool for proposing new research methods. Several articles [1] [2] [3] have proposed similar methods for organic compounds and amino acids.展开更多
The possibility of determining atomic fractions of the isotopes of carbon directly in urea, nitrobenzene, benzophenone, benzoic acid and 2-Hydroxybenzoic acid in compounds isotopically modified by all carbon centers, ...The possibility of determining atomic fractions of the isotopes of carbon directly in urea, nitrobenzene, benzophenone, benzoic acid and 2-Hydroxybenzoic acid in compounds isotopically modified by all carbon centers, as well as by one or several identical carbon centers is considered. The mass peaks of the mass spectrum that allows determining the atomic fraction of carbon isotopes are selected. The respective formulas are proposed. Until now, isotope analysis of these compounds has been carried out by converting them to carbon monoxide or dioxide, and it has been impossible to determine the atomic fraction of carbon at individual centers.展开更多
Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availabil...Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.展开更多
Carbon monosulfide molecular ion (CS+), which plays an important role in various research fields, has long been attracting much interest. Because of the unstable and transient nature of CS+, its electronic states ...Carbon monosulfide molecular ion (CS+), which plays an important role in various research fields, has long been attracting much interest. Because of the unstable and transient nature of CS+, its electronic states have not been well investigated. In this paper, the electronic states of CS+ are studied by employing the internally contracted multireference configuration interaction method, and taking into account relativistic effects (scalar plus spin–orbit coupling). The spin–orbit coupling effects are considered via the state-interacting method with the full Breit–Pauli Hamiltonian. The potential energy curves of 18 Λ–S states correlated with the two lowest dissociation limits of CS+ molecular ion are calculated, and those of 10 lowest Ω states generated from the 6 lowest Λ–S states are also worked out. The spectroscopic constants of the bound states are evaluated, and they are in good agreement with available experimental results and theoretical values. With the aid of analysis of Λ–S composition of Ω states at different bond lengths, the avoided crossing phenomena in the electronic states of CS+ are illuminated. Finally, the single ionization spectra of CS (X1Σ+) populating the CS+(X2Σ1/2+, A2Π3/2, A2Π1/2, and B2Σ1/2+) states are simulated. The vertical ionization potentials for X2Σ1/2+, A2Π3/2, A2Π1/2, and B2Σ1/2+ states are calculated to be 11.257, 12.787, 12.827, and 15.860 eV, respectively, which are accurate compared with previous experimental results, within an error margin of 0.08 eV^0.2 eV.展开更多
The molecular dissociation with a two-laser-pulse scheme is theoretically investigated for the hydrogen molecular ion(H2^+) and its isotopes(HD^+and HT^+). The terahertz pulse is used to steer the electron moti...The molecular dissociation with a two-laser-pulse scheme is theoretically investigated for the hydrogen molecular ion(H2^+) and its isotopes(HD^+and HT^+). The terahertz pulse is used to steer the electron motion after it has been excited by an ultrashort ultraviolet laser pulse and an unprecedented electron localization ratio can be achieved. With the coupled equations, the mass effect of the nuclei on the effective time of the electron localization control is discussed.展开更多
A semi-classical model is utilized to explain the dissociation control of the hydrogen molecular ion (H^-). By ana- lyzing the curve of the dissociation asymmetry parameter as a function of the time delay between th...A semi-classical model is utilized to explain the dissociation control of the hydrogen molecular ion (H^-). By ana- lyzing the curve of the dissociation asymmetry parameter as a function of the time delay between the exciting and steering pulses, we find that the dissociation control is dependent not only on the peak intensity and direction of the electric field of the steering pulse, but also on the peak intensity of the exciting pulse.展开更多
Different from atoms, the multicenter of the Coulombic potentials in molecules makes the tunneling ionization complex,and the electron tunnels out the laser-dressed Coulomb potential with a complex structure. We study...Different from atoms, the multicenter of the Coulombic potentials in molecules makes the tunneling ionization complex,and the electron tunnels out the laser-dressed Coulomb potential with a complex structure. We study tunneling exits of H2^+ at large internuclear distance in strong laser fields by numerically simulating the time-dependent Schrodinger equation plus a classical backward propagation of the ionized wave packet. This study strengthens the understanding of molecular tunneling ionization in strong laser fields.展开更多
This paper utilizes multireference configuration interaction theory to calculate the lifetime of A2Пu state for nitrogen molecular ion N2+. It obtains the transition moment function for A2Пu →X2∑g+, Franck-Condo...This paper utilizes multireference configuration interaction theory to calculate the lifetime of A2Пu state for nitrogen molecular ion N2+. It obtains the transition moment function for A2Пu →X2∑g+, Franck-Condon factors between vibrational levels of the two states. The calculated lifetimes are 16.81, 14.62, 13.10, 12.18, 11.40, and 11.64 its for v′ = 0, 1, 2, 3, 4, 5 vibrational levels of A2Пu state, respectively, which are in excellent agreement with available experimental values.展开更多
Electrical double layer (EDL) capacitors based on recently emergent graphene materials have shown several folds performance improvement compared to conventional porous carbon materials, driving a wave of technology ...Electrical double layer (EDL) capacitors based on recently emergent graphene materials have shown several folds performance improvement compared to conventional porous carbon materials, driving a wave of technology breakthrough in portable and renewable energy storage. Accordingly, much interest has been generated to pursue a comprehensive understanding of the fundamental yet elusive double layer structure at file electrode^electrolyte interface. In this paper, we carried out comprehensive molecular dynamics simulations to obtain a com- prehensive picture of how ion type, solvent properties, and charging conditions affect the EDL structure at the graphene electrode surface, and thereby its contribution to capacitance. We show that different symmetrical monovalent aqueous electrolytes M^X- (M~ = Na~, K~, Rb+, and Cs+; X- = F-, CI-, and I ) indeed have distinctive EDL structures. Larger ions, such as, Rb*, Cs*, C1, and I, undergo partial dehydration and penetrate through the first water layer next to the graphene electrode surfaces under charging. As such, the electrical potential distribution through the EDL strongly depends on the ion type. Interestingly, we further reveal that the water can play a critical role in determining the capacitance value. The change of dielectric constant of water in different electrolytes largely cancels out the variance in electric potential drop across the EDL of different ion type. Our simulation sheds new lights on how the interplay between solvent molecules and EDL structure cooperatively contributes to capacitance, which agrees with our experimental results well.展开更多
We have carried out calculations to search Borromean windows(BWs) for 11 different three-body systems interacting with screened Coulomb(Yukawa-type) potentials using Hylleraas-type wave functions within the framework ...We have carried out calculations to search Borromean windows(BWs) for 11 different three-body systems interacting with screened Coulomb(Yukawa-type) potentials using Hylleraas-type wave functions within the framework of a variational approach. The critical values of the screening parameters for the ground states of the systems under consideration are reported for which the three-body systems are stable, while all the possible fragments are unbound;that is, it shows windows for Borromean binding.展开更多
The hydrogen ion implantation process in Smart-Cut technology is investigated in the present paper using molecular dynamics(MD) simulations.This work focuses on the effects of the implantation energy,dose of hydroge...The hydrogen ion implantation process in Smart-Cut technology is investigated in the present paper using molecular dynamics(MD) simulations.This work focuses on the effects of the implantation energy,dose of hydrogen ions and implantation temperature on the distribution of hydrogen ions and defect rate induced by ion implantation.Numerical analysis shows that implanted hydrogen ions follow an approximate Gaussian distribution which mainly depends on the implantation energy and is independent of the hydrogen ion dose and implantation temperature.By introducing a new parameter of defect rate,the influence of the processing parameters on defect rate is also quantitatively examined.展开更多
In order to illustrate the ion transport mechanism of chloride channel(Cl C) protein,a type of Cl C protein,Cl C-ec1,from Escherichia coli is embedded into an explicit membranewater system by using software VMD. The...In order to illustrate the ion transport mechanism of chloride channel(Cl C) protein,a type of Cl C protein,Cl C-ec1,from Escherichia coli is embedded into an explicit membranewater system by using software VMD. Then a parallel molecular dynamics(MD) simulation is employed to equilibrate the Cl C-ec1 structure for 27.5 ns at temperature 298.15 K. Based on this equilibrated structure,we compute the channel geometric size variation and electrostatic potential distribution along the channel. Meanwhile,Cl^- transport process is simulated using oriented random walk method under variable external potential. The simulation result shows that Cl^- transport velocity depends on the width of the narrowest channel region. Mutation of negative glutamate E148 can produce positive potential,which is beneficial for Cl^- transport,around external Cl^- binding region in the channel. The simulated current-voltage curves about Cl^- transporting in Cl C-ec1 protein agree with Jayaram's experimental results.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11404204the Key Project of the Ministry of Education of China under Grant No 211025+1 种基金the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20111404120004the Natural Science Foundation for Young Scientists of Shanxi Province under Grant No 2009021005
文摘We propose an efficient method for the generation of an isolated attosecond pulse from the asymmetric molecular ions HeH^2+ by adding a half-cycle-like field (HCLF) to the fundamental driving laser field. The high-order harmonic generation (HHG) is investigated by numerically sowing the time-dependent Schrodinger equation. By performing the time-frequency distributions and the electronic wave packet probability densities, we find that the optimizing combined field is not only useful for extending the HHG cutoff, but also for simplifying the recombination channels through controlling the electron localization. In addition, by adjusting the intensity of the HCLF, a dominant short quantum path is selected to contribute the HHG spectrum. As a result, a 75-as isolated attosecond pulse is obtained by superposing a proper range of the harmonics.
基金supported by the National Natural Science Foundation of China(Grants Nos.11474316,11004221,10974224,and 11274348)the"Hundred Talent Program"of Chinese Academy of Sciences+1 种基金supported by NSERC,SHARCnet,ACEnet of Canadathe CAS/SAFEA International Partnership Program for Creative Research Teams
文摘In this paper, we overview recent advances in high-precision structure calculations of the hydrogen molecular ions (H2+ and HD+), including nonrelativistic energy eigenvalues and relativistic and quantum electrodynamic corrections. In combination with high-precision measurements, it is feasible to precisely determine a molecular-based value of the proton- to-electron mass ratio. An experimental scheme is presented for measuring the rovibrational transition frequency (v,L) : (0, 0) → (6,1) in HD+, which is currently underway at the Wuhan Institute of Physics and Mathematics.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974229,11404204,and 11947002)the Scientific and Technological Innovation Program of Higher Education Institutions in Shanxi,China(Grant No.2021L255)。
文摘The high-order harmonic generation from an asymmetric molecular ion is theoretically investigated based on the Born-Oppenheimer model with two-dimensional electron dynamics.It is shown that the harmonic intensity changes periodically in elliptically polarized laser fields.The periodical character is ellipticity-dependent.By establishing the physical image,the periodicity of the harmonic intensity can be ascribed to the contributions of the ground state and the excited state.Furthermore,the electron dynamics from different electronic states can be selected via combining the elliptically polarized laser field with a static electric field.The harmonics dominated either by ground state or excited state are emitted once in an optical cycle in the combined laser field.
基金This work was supported by the Shanghai Priority Academic Discipline, the National Natural Science Foundation of China (No. 10234030 and 10374030)the National Key Project for Basic Research of China (No.1999075204)the Key Project sponsored by Shanghai Science and Technology Committee (No. 036105019and 03DJ14001)the Twilight Project sponsored by Shanghai Education Committee (No. 03SG23)
文摘High-order harmonic generation from one-dimensional (1D) multi-atom molecular ions ill an ultra-short laser field is theoretically- investigated, The dynamics of the electron in a linearly polarized intense laser field is analyzed in terms of 1D Schroedinger equation with the Crank-Nicolson algorithm, The dependence of high-order harmonics on the laser frequeney and the biter-nuclear distance is discussed, It is found that the optimum range of inter-nuclear distance should be changed to get extended harmonic generation for different laser frequency, and the lower frequency laser pulse is favorable to higher order harmonic generation as the inter-nuclear distance increases.
基金Project supported by the National Natural Science Foundation of China(Grant No.11404204)the Key Project of Chinese Ministry of Education(Grant No.211025)+2 种基金the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111404120004)the Natural Science Foundation for Young Scientists of Shanxi Province,China(Grant No.2009021005)the Innovation Project for Postgraduates of Shanxi Province,China(Grant No.20133081)
文摘We theoretically investigate the electron localization around two nuclei in harmonic emission from asymmetric molecular ion. The results show that the ionization process of electron localized around one nucleus competes with its transfer process to the other nucleus. By increasing the initial vibrational level, more electrons localized around the nucleus D+ tend to transfer to the nucleus He2+ so that the ionizations of electrons localized around the nucleus He2+ increase. In this case, the difference in harmonic efficiency between Hell2+ and HeD2+ decreases while the difference in harmonic spectral structure increases. The evident minimum can be observed the spectral structure of HeD2+, which is due to the strong in the harmonic spectrum of Hell2+ compared with that in interference of multiple recombination channels originating from two nuclei. Time-dependent nuclear probability density, electron-nuclear probability density, double-well model, and time-frequency maps are presented to explain the underlying mechanisms.
基金supported by the National Natural Science Foundation of China(Grant Nos.11104180,11175120,11121504,and 11322438)the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China(Grant No.131010)
文摘The photoelectron momentum distribution of H+ in circularly polarized laser fields is studied based on classical trajectory calculations. We screen Coulomb potentials at different radii, and trace trajectories of an ensemble of electrons in such screened Coulomb potentials and circularly polarized laser fields. Simulations show that electron trajectories are bent by Coulomb fields, resulting in the laser-intensity-dependent drift of photoelectron momentum distributions in the laser polarization plane. This study intuitively explains how Coulomb potentials modify photoelectron momenta.
基金Project supported by the National Natural Science Foundation of China(Grant No.11204389)the Natural Science Foundation Project of Chongqing(Grant Nos.CSTC2012jj A50015 and CSTC2012jj A00012)
文摘As an improvement on our previous work [J. Phys. B: At. Mol. Opt. Phys. 45 085101(2012)], an accurate method combining the spheroidal coordinates and B-spline basis is applied to study the ground state 1σg and low excited states1σu, 1πg,u, 1δg,u, 2σg of the H+2in magnetic fields ranging from 10^9Gs(1 Gs = 10^-4T) to 4.414 × 10^13 Gs. Comparing the one-center method used in our previous work, the present method has a higher precision with a shorter computing time.Equilibrium distances of the states of the H+2in strong magnetic fields were found to be accurate to 3-5 significant digits(s.d.) and the total energies 6-11 s.d., even for some antibonding state, such as 1πg, which is difficult for the one-center method to give reliable results while the field strength is B ≥ 10^13 Gs. For the large disagreement in previous works, such as the equilibrium distances of the 1πg state at B = 10^9 Gs, the present data may be used as a reference. Further, the potential energy curves(PECs) and the electronic probability density distributions(EPDDs) of the bound states 1σg, 1πu, 1δg and antibonding states 1σu, 1πg, 1δu for B = 1, 10, 100, 1000 a.u.(atomic unit) are compared, so that the different influences of the magnetic fields on the chemical bonds of the bound states and antibonding states are discussed in detail.
基金supported by the National Natural Science Foundation of China (Grant No. 10604045)the University Science and Technology Planning Program of Shandong Province of China (Grant No. J09LA02)
文摘The photodetachment of a hetero-nuclear diatomic molecular negative ion is studied by using a two-centre model. An analytic formula is presented for the electron flux distribution of a heteronuclear diatomic molecular negative ion. Taking HF- as an example, we calculated the electron flux distributions of this ion for various detached electron energies. The results show that the electron flux distributions exhibit oscillatory structures, which are caused by the interference effect between the two nuclei. Besides, the laser light polarization also has a great influence on the electron flux distribution. The oscillation amplitude is the largest when the laser polarization is parallel to the z-axis; when the laser polarization is perpendicular to the z-axis, the oscillation almost vanishes. This study provides a new understanding of the photodetachment of a heteronuclear diatomic molecular negative ion.
文摘Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can be synthesized either naturally or artificially. To examine the metabolism and regulate the synthesis process, compounds labeled with nitrogen or carbon isotopes need to be used. These isotopic compounds allow for more extensive research and enable studies that would otherwise be impossible. However, their use is dependent on the availability of simple, efficient methods for isotopic analysis. Currently, the determination of the atomic fraction of carbon and nitrogen isotopes is only possible through their conversion into molecular nitrogen or carbon monoxide or carbon dioxide. This leads to the loss of information about isotopic enrichment in specific centers of the molecule. This article explores a new direct approach to determining the atomic fraction of carbon and nitrogen isotopes in the isotope-modified or identical centers of these compounds. This method eliminates the transfer process and dilution due to nitrogen and carbon impurities. It is now possible to simultaneously determine the atomic fraction of nitrogen and carbon isotopes in the research substance. This method can be applied to amino acids, making it an effective tool for proposing new research methods. Several articles [1] [2] [3] have proposed similar methods for organic compounds and amino acids.
文摘The possibility of determining atomic fractions of the isotopes of carbon directly in urea, nitrobenzene, benzophenone, benzoic acid and 2-Hydroxybenzoic acid in compounds isotopically modified by all carbon centers, as well as by one or several identical carbon centers is considered. The mass peaks of the mass spectrum that allows determining the atomic fraction of carbon isotopes are selected. The respective formulas are proposed. Until now, isotope analysis of these compounds has been carried out by converting them to carbon monoxide or dioxide, and it has been impossible to determine the atomic fraction of carbon at individual centers.
文摘Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.
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.11034003,11074095,and 11274140)+1 种基金the Natural Science Foundation of Heilongjiang Province,China(Grant No.QC2011C092)the Scientific Research Fund of Heilongjiang Provincial Education Department,China(Grant No.12531751)
文摘Carbon monosulfide molecular ion (CS+), which plays an important role in various research fields, has long been attracting much interest. Because of the unstable and transient nature of CS+, its electronic states have not been well investigated. In this paper, the electronic states of CS+ are studied by employing the internally contracted multireference configuration interaction method, and taking into account relativistic effects (scalar plus spin–orbit coupling). The spin–orbit coupling effects are considered via the state-interacting method with the full Breit–Pauli Hamiltonian. The potential energy curves of 18 Λ–S states correlated with the two lowest dissociation limits of CS+ molecular ion are calculated, and those of 10 lowest Ω states generated from the 6 lowest Λ–S states are also worked out. The spectroscopic constants of the bound states are evaluated, and they are in good agreement with available experimental results and theoretical values. With the aid of analysis of Λ–S composition of Ω states at different bond lengths, the avoided crossing phenomena in the electronic states of CS+ are illuminated. Finally, the single ionization spectra of CS (X1Σ+) populating the CS+(X2Σ1/2+, A2Π3/2, A2Π1/2, and B2Σ1/2+) states are simulated. The vertical ionization potentials for X2Σ1/2+, A2Π3/2, A2Π1/2, and B2Σ1/2+ states are calculated to be 11.257, 12.787, 12.827, and 15.860 eV, respectively, which are accurate compared with previous experimental results, within an error margin of 0.08 eV^0.2 eV.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,60921004,11134010,11222439,11227902,and 61108012)the National Basic Research Program of China(Grant No.2011CB808103)
文摘The molecular dissociation with a two-laser-pulse scheme is theoretically investigated for the hydrogen molecular ion(H2^+) and its isotopes(HD^+and HT^+). The terahertz pulse is used to steer the electron motion after it has been excited by an ultrashort ultraviolet laser pulse and an unprecedented electron localization ratio can be achieved. With the coupled equations, the mass effect of the nuclei on the effective time of the electron localization control is discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,60921004,11134010,11222439,11227902,and 61108012)the National Key Basic Research Program of China(Grant No.2011CB808103)
文摘A semi-classical model is utilized to explain the dissociation control of the hydrogen molecular ion (H^-). By ana- lyzing the curve of the dissociation asymmetry parameter as a function of the time delay between the exciting and steering pulses, we find that the dissociation control is dependent not only on the peak intensity and direction of the electric field of the steering pulse, but also on the peak intensity of the exciting pulse.
基金Project supported by National Natural Science Foundation of China(Grant Nos.11574205,11327902,and 11421064)the Innovation Program of Shanghai Municipal Education Commission(Grant No.2017-01-07-00-02-E00034)
文摘Different from atoms, the multicenter of the Coulombic potentials in molecules makes the tunneling ionization complex,and the electron tunnels out the laser-dressed Coulomb potential with a complex structure. We study tunneling exits of H2^+ at large internuclear distance in strong laser fields by numerically simulating the time-dependent Schrodinger equation plus a classical backward propagation of the ionized wave packet. This study strengthens the understanding of molecular tunneling ionization in strong laser fields.
基金Project supported by the National Natural Science Foundation of China(Grant No. 10604022)
文摘This paper utilizes multireference configuration interaction theory to calculate the lifetime of A2Пu state for nitrogen molecular ion N2+. It obtains the transition moment function for A2Пu →X2∑g+, Franck-Condon factors between vibrational levels of the two states. The calculated lifetimes are 16.81, 14.62, 13.10, 12.18, 11.40, and 11.64 its for v′ = 0, 1, 2, 3, 4, 5 vibrational levels of A2Пu state, respectively, which are in excellent agreement with available experimental values.
文摘Electrical double layer (EDL) capacitors based on recently emergent graphene materials have shown several folds performance improvement compared to conventional porous carbon materials, driving a wave of technology breakthrough in portable and renewable energy storage. Accordingly, much interest has been generated to pursue a comprehensive understanding of the fundamental yet elusive double layer structure at file electrode^electrolyte interface. In this paper, we carried out comprehensive molecular dynamics simulations to obtain a com- prehensive picture of how ion type, solvent properties, and charging conditions affect the EDL structure at the graphene electrode surface, and thereby its contribution to capacitance. We show that different symmetrical monovalent aqueous electrolytes M^X- (M~ = Na~, K~, Rb+, and Cs+; X- = F-, CI-, and I ) indeed have distinctive EDL structures. Larger ions, such as, Rb*, Cs*, C1, and I, undergo partial dehydration and penetrate through the first water layer next to the graphene electrode surfaces under charging. As such, the electrical potential distribution through the EDL strongly depends on the ion type. Interestingly, we further reveal that the water can play a critical role in determining the capacitance value. The change of dielectric constant of water in different electrolytes largely cancels out the variance in electric potential drop across the EDL of different ion type. Our simulation sheds new lights on how the interplay between solvent molecules and EDL structure cooperatively contributes to capacitance, which agrees with our experimental results well.
基金Supported by the National Natural Science Foundation of China under Grant No.11304086the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province of China under Grant No.UNPYSCT-2015019the Natural Science Foundation for Distinguished Young Scholars in Heilongjiang University under Grant No.JCL201503
文摘We have carried out calculations to search Borromean windows(BWs) for 11 different three-body systems interacting with screened Coulomb(Yukawa-type) potentials using Hylleraas-type wave functions within the framework of a variational approach. The critical values of the screening parameters for the ground states of the systems under consideration are reported for which the three-body systems are stable, while all the possible fragments are unbound;that is, it shows windows for Borromean binding.
基金Project supported by the National Natural Science Foundation of China(No.11372261)the Excellent Young Scientists Supporting Project of Science and Technology Department of Sichuan Province(No.2013JQ0030)+3 种基金the Supporting Project of Department of Education of Sichuan Province(No.2014zd3132)the Opening Project of Key Laboratory of Testing Technology for Manufacturing Process,Southwest University of Science and Technology-Ministry of Education(No.12zxzk02)the Fund of Doctoral Research of Southwest University of Science and Technology(No.12zx7106)the Postgraduate Innovation Fund Project of Southwest University of Science and Technology(No.14ycxjj0121)
文摘The hydrogen ion implantation process in Smart-Cut technology is investigated in the present paper using molecular dynamics(MD) simulations.This work focuses on the effects of the implantation energy,dose of hydrogen ions and implantation temperature on the distribution of hydrogen ions and defect rate induced by ion implantation.Numerical analysis shows that implanted hydrogen ions follow an approximate Gaussian distribution which mainly depends on the implantation energy and is independent of the hydrogen ion dose and implantation temperature.By introducing a new parameter of defect rate,the influence of the processing parameters on defect rate is also quantitatively examined.
基金Supported by the National Natural Science Foundation of China(11304123)the Scientific Research Foundation of Jianghan University(2013016)
文摘In order to illustrate the ion transport mechanism of chloride channel(Cl C) protein,a type of Cl C protein,Cl C-ec1,from Escherichia coli is embedded into an explicit membranewater system by using software VMD. Then a parallel molecular dynamics(MD) simulation is employed to equilibrate the Cl C-ec1 structure for 27.5 ns at temperature 298.15 K. Based on this equilibrated structure,we compute the channel geometric size variation and electrostatic potential distribution along the channel. Meanwhile,Cl^- transport process is simulated using oriented random walk method under variable external potential. The simulation result shows that Cl^- transport velocity depends on the width of the narrowest channel region. Mutation of negative glutamate E148 can produce positive potential,which is beneficial for Cl^- transport,around external Cl^- binding region in the channel. The simulated current-voltage curves about Cl^- transporting in Cl C-ec1 protein agree with Jayaram's experimental results.