The tunneling ionization rates of vibrationally excited N2 molecules at the ground electronic state are calculated using molecular orbital Ammosov–Delone–Krainov theory considering R-dependence. The results show tha...The tunneling ionization rates of vibrationally excited N2 molecules at the ground electronic state are calculated using molecular orbital Ammosov–Delone–Krainov theory considering R-dependence. The results show that molecular alignment significantly affects the ionization rate, as the rate is mainly determined by the electron density distribution of the highest occupied molecular orbital. The present work indicates that the ratios of alignment-dependent rates of different vibrational levels to that of the vibrational ground level increase for the aligned N2 at the angle θ = 0?, and suggests that the alignment-dependent tunneling ionization rates can be used as a diagnostics for the influence of vibrational excitation on the strong field ionization of molecules.展开更多
We derive a simple ionization rate formula for the ground state of a hydrogen atom in the velocity gauge under the conditions:ω〈〈1 a.u.(a.u.is short for atomic unit) and γ〈〈1(ω is the laser frequency and y ...We derive a simple ionization rate formula for the ground state of a hydrogen atom in the velocity gauge under the conditions:ω〈〈1 a.u.(a.u.is short for atomic unit) and γ〈〈1(ω is the laser frequency and y is the Keldysh parameter).Comparisons are made among the different versions of the Keldysh-Faisal-Reiss(KFR) theory.The numerical study shows that with considering the quasi-classical(WKB) Coulomb correction in the final state of the ionized electron,the photoionization rate is enhanced compared with without considering the Coulomb correction,and the Reiss theory with the WKB Coulomb correction gives the correct result in the tunneling regime.Our concise formula of the ionization rate may provide an insight into the ionization mechanism for the ground state of a hydrogen atom.展开更多
The authors found the effect of magnetic field on the ionization of atoms and ions and shown that the magnetic field affected the rate of ionization and electron emission at angle of 60°, 120°, 240° and...The authors found the effect of magnetic field on the ionization of atoms and ions and shown that the magnetic field affected the rate of ionization and electron emission at angle of 60°, 120°, 240° and 300°. It is shown that the calculation must take into account the ionization potential of the magnetic field.展开更多
The influences of the low-emissive graphite segmented electrode t)laeed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle- in-cell method. A two-dimensional phys...The influences of the low-emissive graphite segmented electrode t)laeed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle- in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on the potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with tile increasing of the segmented electrode length, the equipotential lines bend towards the channel exit. and approximately parallel to the wall at the channel surface, the radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of the ionization rate in the discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected.展开更多
In this paper, the radiation losses of impurity on HL-2A have been simulated by assuming the profiles electron temperature and density and solving ionization rate equation under conditions of non-coronal radiation. Th...In this paper, the radiation losses of impurity on HL-2A have been simulated by assuming the profiles electron temperature and density and solving ionization rate equation under conditions of non-coronal radiation. The time required for an impurity species to establish equilibrium is proved to be sensitively dependent on the plasma electron temperature, and it is strongly correlated with the ionization state distribution during equilibrium establishment of impurity species, It is found from simulation results that the residence parameter plays an important role in the enhancement of radiation losses of plasma.展开更多
We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH2+ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schr6dinger e...We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH2+ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schr6dinger equation with B-spline basis. Then the angular dependence of strong-field ionization rates of HeH2+ are investigated with the molecular tunneling ionization theory. We show that the shape of several lowly excited states (i.e. 2pσ, 2pπ, 3dσ) for HeH2+ are reflected in the orientation dependent ionization rates very well, however, the angle-dependent ionization rate fails to follow the angular distribution of the asymptotic electron density for the ground state lsσ. We also show that the internuclear distance dependent ionization probabilities are in a good agreement with the more accurate result obtained from the numerical solution of the time-dependent Schr6dinger equation.展开更多
Ionization rate coefficients and saturation drift velocities for electrons and holes are the vital material parameters in determining the performance of an IMPATT diode.We have performed a sensitivity analysis of the ...Ionization rate coefficients and saturation drift velocities for electrons and holes are the vital material parameters in determining the performance of an IMPATT diode.We have performed a sensitivity analysis of the millimeter wave characteristics of 4H-SiC and 6H-SiC IMPATT diodes with reference to the above mentioned material data and an operating frequency of 220 GHz.The effect of a small variation in the ionization rate and drift velocity on the device characteristics like break down voltage,efficiency,noise measure and power output has been presented here.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922200)the National Natural Science Foundation of China(Grant Nos.11034003 and 11127403)
文摘The tunneling ionization rates of vibrationally excited N2 molecules at the ground electronic state are calculated using molecular orbital Ammosov–Delone–Krainov theory considering R-dependence. The results show that molecular alignment significantly affects the ionization rate, as the rate is mainly determined by the electron density distribution of the highest occupied molecular orbital. The present work indicates that the ratios of alignment-dependent rates of different vibrational levels to that of the vibrational ground level increase for the aligned N2 at the angle θ = 0?, and suggests that the alignment-dependent tunneling ionization rates can be used as a diagnostics for the influence of vibrational excitation on the strong field ionization of molecules.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274149 and 11304185)the Program of Shenyang Key Laboratory of Optoelectronic Materials and Technology,China(Grant No.F12-254-1-00)
文摘We derive a simple ionization rate formula for the ground state of a hydrogen atom in the velocity gauge under the conditions:ω〈〈1 a.u.(a.u.is short for atomic unit) and γ〈〈1(ω is the laser frequency and y is the Keldysh parameter).Comparisons are made among the different versions of the Keldysh-Faisal-Reiss(KFR) theory.The numerical study shows that with considering the quasi-classical(WKB) Coulomb correction in the final state of the ionized electron,the photoionization rate is enhanced compared with without considering the Coulomb correction,and the Reiss theory with the WKB Coulomb correction gives the correct result in the tunneling regime.Our concise formula of the ionization rate may provide an insight into the ionization mechanism for the ground state of a hydrogen atom.
文摘The authors found the effect of magnetic field on the ionization of atoms and ions and shown that the magnetic field affected the rate of ionization and electron emission at angle of 60°, 120°, 240° and 300°. It is shown that the calculation must take into account the ionization potential of the magnetic field.
基金supported by National Natural Science Foundation of China(Nos.11375039 and 11275034)the Key Project of Science and Technology of Liaoning Province,China(No.2011224007)the Fundamental Research Funds for the Central Universities,China(No.3132014328)
文摘The influences of the low-emissive graphite segmented electrode t)laeed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle- in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on the potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with tile increasing of the segmented electrode length, the equipotential lines bend towards the channel exit. and approximately parallel to the wall at the channel surface, the radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of the ionization rate in the discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected.
文摘In this paper, the radiation losses of impurity on HL-2A have been simulated by assuming the profiles electron temperature and density and solving ionization rate equation under conditions of non-coronal radiation. The time required for an impurity species to establish equilibrium is proved to be sensitively dependent on the plasma electron temperature, and it is strongly correlated with the ionization state distribution during equilibrium establishment of impurity species, It is found from simulation results that the residence parameter plays an important role in the enhancement of radiation losses of plasma.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11164025,11044007,11064013the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant Nos.20096203110001,20116203120001the Foundation of Northwest Normal University under Grant No.NWNU-KJCXGC-03-62
文摘We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH2+ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schr6dinger equation with B-spline basis. Then the angular dependence of strong-field ionization rates of HeH2+ are investigated with the molecular tunneling ionization theory. We show that the shape of several lowly excited states (i.e. 2pσ, 2pπ, 3dσ) for HeH2+ are reflected in the orientation dependent ionization rates very well, however, the angle-dependent ionization rate fails to follow the angular distribution of the asymptotic electron density for the ground state lsσ. We also show that the internuclear distance dependent ionization probabilities are in a good agreement with the more accurate result obtained from the numerical solution of the time-dependent Schr6dinger equation.
文摘Ionization rate coefficients and saturation drift velocities for electrons and holes are the vital material parameters in determining the performance of an IMPATT diode.We have performed a sensitivity analysis of the millimeter wave characteristics of 4H-SiC and 6H-SiC IMPATT diodes with reference to the above mentioned material data and an operating frequency of 220 GHz.The effect of a small variation in the ionization rate and drift velocity on the device characteristics like break down voltage,efficiency,noise measure and power output has been presented here.