The dipole-length, dipole-velocity and dipole-acceleration absorption oscillator strengths for the 1s^22s-1s^2np (3 ≤ n ≤9) transitions of lithium-like systems from Z = 11 to 20 are calculated by using the energie...The dipole-length, dipole-velocity and dipole-acceleration absorption oscillator strengths for the 1s^22s-1s^2np (3 ≤ n ≤9) transitions of lithium-like systems from Z = 11 to 20 are calculated by using the energies and the multiconfiguration interaction wave functions obtained from a full core plus correlation method, in which relativistic and mass-polarization effects on the energy, as the first-order perturbation corrections, are included. The results of three forms are in good agreement with each other, and closely agree with the experimental data available in the literature. Based on the quantum defects obtained with quantum defect theory (QDT), the discrete oscillator strengths for the transitions from the ground state to highly excited states 1s^2np (n ≥ 10) and oscillator strength densities corresponding to the bound-free transitions are obtained for these ions.展开更多
The transition energies, E1 transitional oscillator strengths of the spin-allowed as well as the spin-forbidden and the corresponding transition rates, and complete M1, E2, M2 forbidden transition rates for 1s^(2), 1s...The transition energies, E1 transitional oscillator strengths of the spin-allowed as well as the spin-forbidden and the corresponding transition rates, and complete M1, E2, M2 forbidden transition rates for 1s^(2), 1s2s, and 1s2p states of He I, are investigated using the multi-configuration Dirac–Hartree–Fock method. In the subsequent relativistic configuration interaction computations, the Breit interaction and the QED effect are considered as perturbation, separately. Our transition energies, oscillator strengths, and transition rates are in good agreement with the experimental and other theoretical results. As a result, the QED effect is not important for helium atoms, however, the effect of the Breit interaction plays a significant role in the transition energies, the oscillator strengths and transition rates.展开更多
The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix method.We obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoo...The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix method.We obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering matrices.By employing the MQDT,all discrete energy levels for N could be calculated accurately without missing anyone.The MQDT parameters(i.e.,scattering matrices)can be calibrated with the available precise spectroscopy values.In this work,the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained,which provide rich data for the diagnostic analysis of plasma.展开更多
The P XIII spectrum has been analyzed by several authors using different light sources. The semi-empirical oscillator strengths (gf) and the lifetimes presented in this work for all known P XIII spectral lines and ene...The P XIII spectrum has been analyzed by several authors using different light sources. The semi-empirical oscillator strengths (gf) and the lifetimes presented in this work for all known P XIII spectral lines and energy levels were carried out in a multi-configuration Hartree-Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure in order to improve the adjustment of theoretical to experimental energy levels. The method produces gf-values that are in agreement with intensity observations and lifetime values closer to the experimental ones.展开更多
The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence...The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ←4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. (Phys. Rev. A 67 022703 (2003)). The differences between the experimental results and theoretical calculations show that more studies are needed.展开更多
The oscillator strengths of the absorption spectra for rare earth complexes in different solvents were determined and calculated on the basis of the JuddOfelt theory. The effect of different ligand field strengths on ...The oscillator strengths of the absorption spectra for rare earth complexes in different solvents were determined and calculated on the basis of the JuddOfelt theory. The effect of different ligand field strengths on the oscillator strengths of lanthanide ions is discussed. In plotting the oscillator strengths of the hypersensitive transition of Ho3+, Er3+ against those of Nd3+, the reverse extending lines of the straight lines were found to intersect at a point on the whole. The coordinates of the crosspoint are believed to represent the strength value of the smallest coordinated effect.展开更多
Oscillator strengths and cross sections of the valence-shell excitations in NO_(2)are of great significance in testing the theoretical calculations and monitoring the state of the ozone layer in the earth’s atmospher...Oscillator strengths and cross sections of the valence-shell excitations in NO_(2)are of great significance in testing the theoretical calculations and monitoring the state of the ozone layer in the earth’s atmosphere. In the present work, the generalized oscillator strengths of the valence-shell excitations in NO_(2)were obtained based on the fast electron scattering technique at an incident electron energy of 1.5 ke V and an energy resolution of about 70 me V. By extrapolating the generalized oscillator strengths to the limit of a zero squared momentum transfer, the optical oscillator strengths for the dipole-allowed transitions have been obtained, which provide an independent cross check to the previous experimental results. Based on the BE-scaling method, the corresponding integral cross sections have also been derived systematically from the excitation threshold to 5000 eV. The present dynamic parameters can provide the fundamental spectroscopic data of NO_(2)and have important applications in the studies of atmospheric science. The datasets presented in this paper, including the GOSs, OOSs and ICSs, are openly available at https://doi.org/10.57760/sciencedb.j00113.00156.展开更多
The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic effe...The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic effect.It is found that the vibronic effect converts the dipole-forbidden excitation of the ^(1)A_(2) into a dipole-allowed one,which enhances the intensities of the corresponding generalized oscillator strength in the small squared momentum transfer region.The present investigation shows that the vibronic effect of H_(2)O is slightly stronger than that of D_(2)O,which exhibits a clear isotopic effect.展开更多
We report electronic properties of a hydrogen atom encaged by an endohedral cavity under the influence of a weak plasma interaction. Weimplement a finite-difference approach to solve the Schrodinger equation for a hyd...We report electronic properties of a hydrogen atom encaged by an endohedral cavity under the influence of a weak plasma interaction. Weimplement a finite-difference approach to solve the Schrodinger equation for a hydrogen atom embedded in an endohedral cavity modeled by theWoods-Saxon potential with well depth V0, inner radius R0, thickness D, and smooth parameter g. The plasma interaction is described by aDebye-Hu¨ckel screening potential that characterizes the plasma in terms of a Debye screening length lD. The electronic properties of theendohedral hydrogen atom are reported for selected endohedral cavity well depths, V0, and screening lengths, lD, that emulate differentconfinement and plasma conditions. We find that for low screening lengths, the endohedral cavity potential dominates over the plasma interaction by confining the electron within the cavity. For large screening lengths, a competition between both interactions is observed. We assessand report the photo-ionization cross section, dipole polarizability, mean excitation energy, and electronic stopping cross section as function of lD and V0. We find a decrease of the Generalized Oscillator Strength (GOS) when the final excitation is to an s state as the plasma screeninglength decreases. For a final excitation into a p state, we find an increase in the GOS as the endohedral cavity well-depth increases. For the caseof the electronic stopping cross section, we find that the plasma screening and endohedral cavity effects are larger in the low-to-intermediateprojectile energies for all potential well depths considered. Our results agree well to available theoretical and experimental data and are afirst step towards the understanding of dipole and generalized oscillator strength dependent properties of an atom in extreme conditions encagedby an endohedral cavity immersed in a plasma medium.展开更多
We consider the D-dimensional SchrSdinger equation under the hyperbolic potential V0(1 -coth(ar))+ 171 (1 - coth(ar))2. Using a Pekeris-type approximation, the approximate analytical solutions of the problem ...We consider the D-dimensional SchrSdinger equation under the hyperbolic potential V0(1 -coth(ar))+ 171 (1 - coth(ar))2. Using a Pekeris-type approximation, the approximate analytical solutions of the problem are obtained via the supersymmetric quantum mechanics. The behaviors of energy eigenvalues versus dimension are discussed for various quantum numbers. Useful expectation values as well as the oscillator strength are obtained.展开更多
Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration-interaction method, calculations of transition energies, oscillator strengths and rates are performed for the 3s...Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration-interaction method, calculations of transition energies, oscillator strengths and rates are performed for the 3s2 1S0-3s3p 1P1 spinallowed transition, 3s2 1S0-3s3p 3P1,2 intercombination and magnetic quadrupole transition in the Mg isoelectronic sequence (Mg I, A1 II, Si III, P IV and S V). Electron correlations are treated adequately, including intravalence electron correlations. The influence of the Breit interaction on oscillator strengths and transition energies are investigated. Quantum eleetrodynamics corrections are added as corrections. The calculation results are found to be in good agreement with the experimental data and other theoretical calculations.展开更多
This paper presents a review about the radiative properties (transition probabilities and oscillator strengths) of two xenon ions (Xe<sup>9+</sup>, Xe<sup>10+</sup>) and three members of Er I i...This paper presents a review about the radiative properties (transition probabilities and oscillator strengths) of two xenon ions (Xe<sup>9+</sup>, Xe<sup>10+</sup>) and three members of Er I isoelectronic sequence (Lu<sup>3+</sup>, Hf<sup>4+</sup>, Ta<sup>5+</sup>) of interest in controlled thermonuclear fusion, including our recent theoretical data obtained using two independent theoretical atomic structure computational approaches (semi-empirical Hartree-Fock with relativistic corrections method (HFR) and the <em>ab initio</em> multiconfiguration Dirac-Hartree-Fock (MCDHF)). The tables, from the second one, summarize the recommended data expected to be useful for plasma modelling in fusion.展开更多
Photoacoustic (PA) spectra of powdered neodymium oxide (Nd 2O 3 (A type)), neodymium hydrated chloride (NdCl 3·6H 2O) and neodymium fluoride (NdF 3) were reported. PA band shifts as compared to their positio...Photoacoustic (PA) spectra of powdered neodymium oxide (Nd 2O 3 (A type)), neodymium hydrated chloride (NdCl 3·6H 2O) and neodymium fluoride (NdF 3) were reported. PA band shifts as compared to their positions in aqueous Nd 3+ are used to calculate the nephelauxetic parameters of the compounds. The variation of these parameters and correlation with the nature of metal ligand bonding were discussed. A novel method is introduced to determine the relative values of oscillator strengths and Judd Ofelt parameters of powdered samples using PA spectroscopy. It is found that a linear correlation exists between relative values of τ 2 and oscillator strengths of hypersensitive transitions of the title compounds. It is hopetul that the new method of PA technique may serve for the Judd Ofelt quantitative analysis of powdered rare earth compounds.展开更多
Strain effects on the polarized optical properties of c-plane and m-plane InxGa1-xN were discussed for different In compositions (x = 0, 0.05, 0.10, 0.15) by analyzing the relative oscillator strength (ROS) and en...Strain effects on the polarized optical properties of c-plane and m-plane InxGa1-xN were discussed for different In compositions (x = 0, 0.05, 0.10, 0.15) by analyzing the relative oscillator strength (ROS) and energy level splitting of the three transitions related to the top three valence bands (VBs). The ROS was calculated by applying the effective-mass Hamiltonian based on k .p perturbation theory. For c-plane InxGa1-xN, it was found that the ROS of 〈X〉 and 〈Y〉-like states were superposed with each other. Especially, under compressive strain, they dominated in the top VB whose energy level also went up with strain, while the ROS of the |Z〉-like state decreased in the second band. For m-plane InxGa1-xN under compressive strain, the top three VBs were dominated by 〈X〉, 〈Z〉, and 〈Y〉-like states, respectively, which led to nearly linearly-polarized light emissions. For the top VB, ROS difference between [X) and [Z)-like states became larger with compressive strain. It was also found that such tendencies were more evident in layers with higher In compositions. As a result, there would be more TE modes in total emissions from both c-plane and m-plane InGaN with compressive strain and In content, leading to a larger polarization degree. Experimental results of luminescence from InGaN/GaN quantum wells (QWs) showed good coincidence with our calculations.展开更多
Absolute optical oscillator strength density and double differential cross section spectra of CO below 120 eV are determined by fast electron impact. Some peaks above the first ionization threshold stand out as the mo...Absolute optical oscillator strength density and double differential cross section spectra of CO below 120 eV are determined by fast electron impact. Some peaks above the first ionization threshold stand out as the momentum transfer square K2 increases. The doubly excited Rydberg states converging to C 2∑^+, D ^2∏, and F ^2∏ states of CO^+, respectively, are confirmed in our spectra. Another peak at around 32eV is assigned to the transition of (3σ)^-1(2π)^1^1∏←X^1∑^+.展开更多
The magnetic field-dependent heavy hole excitonic states in a strained Gao.2Ino.sAs/GaAs quantum dot are investi- gated by taking into account the anisotropy, non-parabolicity of the conduction band, and the geometric...The magnetic field-dependent heavy hole excitonic states in a strained Gao.2Ino.sAs/GaAs quantum dot are investi- gated by taking into account the anisotropy, non-parabolicity of the conduction band, and the geometrical confinement. The strained quantum dot is considered as a parabolic dot of InAs embedded in a GaAs barrier material. The dependence of the effective excitonic g-factor as a function of dot radius and the magnetic field strength is numerically measured. The interband optical transition energy as a function of geometrical confinement is computed in the presence of a mag- netic field. The magnetic field-dependent oscillator strength of interband transition under the geometrical confinement is studied. The exchange enhancements as a function of dot radius are observed for various magnetic field strengths in a strained Gao.2Ino.sAs/GaAs quantum dot. Heavy hole excitonic absorption spectra, the changes in refractive index, and the third-order susceptibility of third-order harmonic generation are investigated in the Gao.2Ino.8As/GaAs quantum dot. The result shows that the effect of magnetic field strength is more strongly dependent on the nonlinear optical property in a low-dimensional semiconductor system.展开更多
The binding energy of an exciton in a wurtzite GaN/GaAlN strained cylindrical quantum dot is investigated theoretically. The strong built-in electric field due to the spontaneous and piezoelectric polarizations of a G...The binding energy of an exciton in a wurtzite GaN/GaAlN strained cylindrical quantum dot is investigated theoretically. The strong built-in electric field due to the spontaneous and piezoelectric polarizations of a GaN/GaAlN quantum dot is included. Numerical calculations are performed using a variational procedure within the single band effective mass approximation. Valence-band anisotropy is included in our theoretical model by using different hole masses in different spatial directions. The exciton oscillator strength and the exciton lifetime for radiative recombination each as a function of dot radius have been computed. The result elucidates that the strong built-in electric field influences the oscillator strength and the recombination life time of the exciton. It is observed that the ground state exciton binding energy and the interband emission energy increase when the cylindrical quantum dot height or radius is decreased, and that the exciton binding energy, the oscillator strength and the radiative lifetime each as a function of structural parameters (height and radius) sensitively depend on the strong built-in electric field. The obtained results are useful for the design of some opto-photoelectronic devices.展开更多
Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong bulk-in electric field (BEF) in strained w...Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong bulk-in electric field (BEF) in strained wurtzite ZnO/Mgo.25Zno.750 quantum dots (QDs), the optical properties of ionized donor-bound excitons (D^+, X) are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of (D^+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of (D^+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth.展开更多
This study considered the design of an efficient, high brightness polar InGaN/GaN light emitting diode (LED) structure with A1GaN capping layer for green light emission. The deposition of high In (〉 15%) composit...This study considered the design of an efficient, high brightness polar InGaN/GaN light emitting diode (LED) structure with A1GaN capping layer for green light emission. The deposition of high In (〉 15%) composition within InGaN quantum well (QW) has limitations when providing intense green light. To design an effective model for a highly efficient InGaN green LEDs, this study considered the compositions of indium and aluminum for InxGal xN QW and AlyGal yN cap layers, along with different layer thicknesses of well, barrier and cap. These structural properties significantly affect different properties. For example, these properties affect electric fields of layers, polarization, overall elastic stress energy and lattice parameter of the structure, emission wavelength, and intensity of the emitted light. Three models with different composition and layer thicknesses are simulated and analyzed to obtain green light with in-plane equilibrium lattice parameter close to GaN (3.189 A ) with the highest oscillator strength values. A structure model is obtained with an oscillator strength value of 1.18 × 10-1 and least in-plane equilibrium lattice constant of 3.218 A. This emitter can emit at a wavelength of 540 nm, which is the expected design for the fabrication of highly efficient, bright green LEDs.展开更多
Hybridized local and charge-transfer(HLCT)excitedstate fluorophores,which enable full exciton utilization through a reverse intersystem crossing fromhigh-lying triplet states to singlet state,have attracted increasing...Hybridized local and charge-transfer(HLCT)excitedstate fluorophores,which enable full exciton utilization through a reverse intersystem crossing fromhigh-lying triplet states to singlet state,have attracted increasing attention toward organic light-emitting diodes(OLEDs)application.Herein,we report three D-π-A-π-D-type isomers o-2CzBT,m-2CzBT,and p-2CzBT by adjusting the donor(D)units from ortho-,meta-,to para-substituted positions with the acceptor(A)core unit,respectively.The HLCT properties of the three compounds are evidently confirmed by theoretical calculations,solvatochromic behaviors,and transient decay lifetimes analyses.As the substituted position changes from the ortho-,meta-,and para-positions,the reduced steric hindrance brings about decreased torsional angle between D and A moieties,resulting in increased oscillator strength.Accordingly,the parasubstituted p-2CzBT is endowed with a more locally excited component that accounts for faster radiative decay,leading to a higher fluorescent efficiency than that of o-2CzBT and m-2CzBT.As expected,p-2CzBT enables its nondoped and doped OLEDs with higher external quantum efficiencies(EQEs)of 12.3% and 15.0%,respectively,which are among the state-ofthe-art efficiencies of HLCT-based OLEDs.Moreover,o-2CzBT and m-2CzBT are also utilized as host materials for high-performance OLEDs,thus extending the application of HLCT materials.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 10774063)
文摘The dipole-length, dipole-velocity and dipole-acceleration absorption oscillator strengths for the 1s^22s-1s^2np (3 ≤ n ≤9) transitions of lithium-like systems from Z = 11 to 20 are calculated by using the energies and the multiconfiguration interaction wave functions obtained from a full core plus correlation method, in which relativistic and mass-polarization effects on the energy, as the first-order perturbation corrections, are included. The results of three forms are in good agreement with each other, and closely agree with the experimental data available in the literature. Based on the quantum defects obtained with quantum defect theory (QDT), the discrete oscillator strengths for the transitions from the ground state to highly excited states 1s^2np (n ≥ 10) and oscillator strength densities corresponding to the bound-free transitions are obtained for these ions.
基金Supported by the National Key Research and Development Program of China (Grant No. 2017YFA0402300)the National Natural Science Foundation of China (Grant Nos. 11774344 and 11474033)。
文摘The transition energies, E1 transitional oscillator strengths of the spin-allowed as well as the spin-forbidden and the corresponding transition rates, and complete M1, E2, M2 forbidden transition rates for 1s^(2), 1s2s, and 1s2p states of He I, are investigated using the multi-configuration Dirac–Hartree–Fock method. In the subsequent relativistic configuration interaction computations, the Breit interaction and the QED effect are considered as perturbation, separately. Our transition energies, oscillator strengths, and transition rates are in good agreement with the experimental and other theoretical results. As a result, the QED effect is not important for helium atoms, however, the effect of the Breit interaction plays a significant role in the transition energies, the oscillator strengths and transition rates.
基金Project supported by the Science Challenge Project(Grant No.TZ2016005)the National Key Research and Development Program of China(Grant Nos.2017YFA0403200 and 2017YFA0402300)the CAEP Foundation(Grant No.CX2019022)。
文摘The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix method.We obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering matrices.By employing the MQDT,all discrete energy levels for N could be calculated accurately without missing anyone.The MQDT parameters(i.e.,scattering matrices)can be calibrated with the available precise spectroscopy values.In this work,the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained,which provide rich data for the diagnostic analysis of plasma.
文摘The P XIII spectrum has been analyzed by several authors using different light sources. The semi-empirical oscillator strengths (gf) and the lifetimes presented in this work for all known P XIII spectral lines and energy levels were carried out in a multi-configuration Hartree-Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure in order to improve the adjustment of theoretical to experimental energy levels. The method produces gf-values that are in agreement with intensity observations and lifetime values closer to the experimental ones.
基金Project supported by the National Natural Science Foundation of China (Grant No 10474089).
文摘The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ←4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. (Phys. Rev. A 67 022703 (2003)). The differences between the experimental results and theoretical calculations show that more studies are needed.
文摘The oscillator strengths of the absorption spectra for rare earth complexes in different solvents were determined and calculated on the basis of the JuddOfelt theory. The effect of different ligand field strengths on the oscillator strengths of lanthanide ions is discussed. In plotting the oscillator strengths of the hypersensitive transition of Ho3+, Er3+ against those of Nd3+, the reverse extending lines of the straight lines were found to intersect at a point on the whole. The coordinates of the crosspoint are believed to represent the strength value of the smallest coordinated effect.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2022YFA1602500)the National Natural Science Foundation of China (Grant Nos. 12334010 and U1932207)。
文摘Oscillator strengths and cross sections of the valence-shell excitations in NO_(2)are of great significance in testing the theoretical calculations and monitoring the state of the ozone layer in the earth’s atmosphere. In the present work, the generalized oscillator strengths of the valence-shell excitations in NO_(2)were obtained based on the fast electron scattering technique at an incident electron energy of 1.5 ke V and an energy resolution of about 70 me V. By extrapolating the generalized oscillator strengths to the limit of a zero squared momentum transfer, the optical oscillator strengths for the dipole-allowed transitions have been obtained, which provide an independent cross check to the previous experimental results. Based on the BE-scaling method, the corresponding integral cross sections have also been derived systematically from the excitation threshold to 5000 eV. The present dynamic parameters can provide the fundamental spectroscopic data of NO_(2)and have important applications in the studies of atmospheric science. The datasets presented in this paper, including the GOSs, OOSs and ICSs, are openly available at https://doi.org/10.57760/sciencedb.j00113.00156.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12334010,12174259,and 11604003)。
文摘The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic effect.It is found that the vibronic effect converts the dipole-forbidden excitation of the ^(1)A_(2) into a dipole-allowed one,which enhances the intensities of the corresponding generalized oscillator strength in the small squared momentum transfer region.The present investigation shows that the vibronic effect of H_(2)O is slightly stronger than that of D_(2)O,which exhibits a clear isotopic effect.
基金This work was supported by grants DGAPA-UNAM PAPIIT-IN-106-617 and LANCAD-UNAM-DGTIC-228 granted to RCT.CMF would like to thank CONACyT scholarship with CVU 424130.
文摘We report electronic properties of a hydrogen atom encaged by an endohedral cavity under the influence of a weak plasma interaction. Weimplement a finite-difference approach to solve the Schrodinger equation for a hydrogen atom embedded in an endohedral cavity modeled by theWoods-Saxon potential with well depth V0, inner radius R0, thickness D, and smooth parameter g. The plasma interaction is described by aDebye-Hu¨ckel screening potential that characterizes the plasma in terms of a Debye screening length lD. The electronic properties of theendohedral hydrogen atom are reported for selected endohedral cavity well depths, V0, and screening lengths, lD, that emulate differentconfinement and plasma conditions. We find that for low screening lengths, the endohedral cavity potential dominates over the plasma interaction by confining the electron within the cavity. For large screening lengths, a competition between both interactions is observed. We assessand report the photo-ionization cross section, dipole polarizability, mean excitation energy, and electronic stopping cross section as function of lD and V0. We find a decrease of the Generalized Oscillator Strength (GOS) when the final excitation is to an s state as the plasma screeninglength decreases. For a final excitation into a p state, we find an increase in the GOS as the endohedral cavity well-depth increases. For the caseof the electronic stopping cross section, we find that the plasma screening and endohedral cavity effects are larger in the low-to-intermediateprojectile energies for all potential well depths considered. Our results agree well to available theoretical and experimental data and are afirst step towards the understanding of dipole and generalized oscillator strength dependent properties of an atom in extreme conditions encagedby an endohedral cavity immersed in a plasma medium.
文摘We consider the D-dimensional SchrSdinger equation under the hyperbolic potential V0(1 -coth(ar))+ 171 (1 - coth(ar))2. Using a Pekeris-type approximation, the approximate analytical solutions of the problem are obtained via the supersymmetric quantum mechanics. The behaviors of energy eigenvalues versus dimension are discussed for various quantum numbers. Useful expectation values as well as the oscillator strength are obtained.
基金supported by the Key Program of Science and Technology Research of Ministry of Education of China (Grant No. 306020)the National Natural Science Foundation of China (Grant Nos. 10905040 and 10734040)+2 种基金the National High-Tech ICF Committee in Chinathe Yin-He Super-computer Center,Institute of Applied Physics and Mathematics,Beijing,Chinathe National Basic Research Program of China (Grant Nos. 2010CB922900 and 2011CB921501)
文摘Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration-interaction method, calculations of transition energies, oscillator strengths and rates are performed for the 3s2 1S0-3s3p 1P1 spinallowed transition, 3s2 1S0-3s3p 3P1,2 intercombination and magnetic quadrupole transition in the Mg isoelectronic sequence (Mg I, A1 II, Si III, P IV and S V). Electron correlations are treated adequately, including intravalence electron correlations. The influence of the Breit interaction on oscillator strengths and transition energies are investigated. Quantum eleetrodynamics corrections are added as corrections. The calculation results are found to be in good agreement with the experimental data and other theoretical calculations.
文摘This paper presents a review about the radiative properties (transition probabilities and oscillator strengths) of two xenon ions (Xe<sup>9+</sup>, Xe<sup>10+</sup>) and three members of Er I isoelectronic sequence (Lu<sup>3+</sup>, Hf<sup>4+</sup>, Ta<sup>5+</sup>) of interest in controlled thermonuclear fusion, including our recent theoretical data obtained using two independent theoretical atomic structure computational approaches (semi-empirical Hartree-Fock with relativistic corrections method (HFR) and the <em>ab initio</em> multiconfiguration Dirac-Hartree-Fock (MCDHF)). The tables, from the second one, summarize the recommended data expected to be useful for plasma modelling in fusion.
文摘Photoacoustic (PA) spectra of powdered neodymium oxide (Nd 2O 3 (A type)), neodymium hydrated chloride (NdCl 3·6H 2O) and neodymium fluoride (NdF 3) were reported. PA band shifts as compared to their positions in aqueous Nd 3+ are used to calculate the nephelauxetic parameters of the compounds. The variation of these parameters and correlation with the nature of metal ligand bonding were discussed. A novel method is introduced to determine the relative values of oscillator strengths and Judd Ofelt parameters of powdered samples using PA spectroscopy. It is found that a linear correlation exists between relative values of τ 2 and oscillator strengths of hypersensitive transitions of the title compounds. It is hopetul that the new method of PA technique may serve for the Judd Ofelt quantitative analysis of powdered rare earth compounds.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60676032,60577030 and 60776042)National Key Basic Research Special Foundation of China (Grant No TG 2007CB307004)
文摘Strain effects on the polarized optical properties of c-plane and m-plane InxGa1-xN were discussed for different In compositions (x = 0, 0.05, 0.10, 0.15) by analyzing the relative oscillator strength (ROS) and energy level splitting of the three transitions related to the top three valence bands (VBs). The ROS was calculated by applying the effective-mass Hamiltonian based on k .p perturbation theory. For c-plane InxGa1-xN, it was found that the ROS of 〈X〉 and 〈Y〉-like states were superposed with each other. Especially, under compressive strain, they dominated in the top VB whose energy level also went up with strain, while the ROS of the |Z〉-like state decreased in the second band. For m-plane InxGa1-xN under compressive strain, the top three VBs were dominated by 〈X〉, 〈Z〉, and 〈Y〉-like states, respectively, which led to nearly linearly-polarized light emissions. For the top VB, ROS difference between [X) and [Z)-like states became larger with compressive strain. It was also found that such tendencies were more evident in layers with higher In compositions. As a result, there would be more TE modes in total emissions from both c-plane and m-plane InGaN with compressive strain and In content, leading to a larger polarization degree. Experimental results of luminescence from InGaN/GaN quantum wells (QWs) showed good coincidence with our calculations.
基金Project supported by the National Nature Science Foundation of China (Grant Nos 10474089, 10134010 and 10004010).
文摘Absolute optical oscillator strength density and double differential cross section spectra of CO below 120 eV are determined by fast electron impact. Some peaks above the first ionization threshold stand out as the momentum transfer square K2 increases. The doubly excited Rydberg states converging to C 2∑^+, D ^2∏, and F ^2∏ states of CO^+, respectively, are confirmed in our spectra. Another peak at around 32eV is assigned to the transition of (3σ)^-1(2π)^1^1∏←X^1∑^+.
文摘The magnetic field-dependent heavy hole excitonic states in a strained Gao.2Ino.sAs/GaAs quantum dot are investi- gated by taking into account the anisotropy, non-parabolicity of the conduction band, and the geometrical confinement. The strained quantum dot is considered as a parabolic dot of InAs embedded in a GaAs barrier material. The dependence of the effective excitonic g-factor as a function of dot radius and the magnetic field strength is numerically measured. The interband optical transition energy as a function of geometrical confinement is computed in the presence of a mag- netic field. The magnetic field-dependent oscillator strength of interband transition under the geometrical confinement is studied. The exchange enhancements as a function of dot radius are observed for various magnetic field strengths in a strained Gao.2Ino.sAs/GaAs quantum dot. Heavy hole excitonic absorption spectra, the changes in refractive index, and the third-order susceptibility of third-order harmonic generation are investigated in the Gao.2Ino.8As/GaAs quantum dot. The result shows that the effect of magnetic field strength is more strongly dependent on the nonlinear optical property in a low-dimensional semiconductor system.
基金Project supported by the University Grants Commission,India (Grant No.38-8/2009(SR))
文摘The binding energy of an exciton in a wurtzite GaN/GaAlN strained cylindrical quantum dot is investigated theoretically. The strong built-in electric field due to the spontaneous and piezoelectric polarizations of a GaN/GaAlN quantum dot is included. Numerical calculations are performed using a variational procedure within the single band effective mass approximation. Valence-band anisotropy is included in our theoretical model by using different hole masses in different spatial directions. The exciton oscillator strength and the exciton lifetime for radiative recombination each as a function of dot radius have been computed. The result elucidates that the strong built-in electric field influences the oscillator strength and the recombination life time of the exciton. It is observed that the ground state exciton binding energy and the interband emission energy increase when the cylindrical quantum dot height or radius is decreased, and that the exciton binding energy, the oscillator strength and the radiative lifetime each as a function of structural parameters (height and radius) sensitively depend on the strong built-in electric field. The obtained results are useful for the design of some opto-photoelectronic devices.
基金Project supported by the National Natural Science Foundation for Young Scientists of China(No.11102100)the Program for New Century Excellent Talents in Fujian Province University(No.JA14285)the Program for Young Top-Notch Innovative Talents of Fujian Province of China
文摘Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong bulk-in electric field (BEF) in strained wurtzite ZnO/Mgo.25Zno.750 quantum dots (QDs), the optical properties of ionized donor-bound excitons (D^+, X) are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of (D^+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of (D^+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth.
文摘This study considered the design of an efficient, high brightness polar InGaN/GaN light emitting diode (LED) structure with A1GaN capping layer for green light emission. The deposition of high In (〉 15%) composition within InGaN quantum well (QW) has limitations when providing intense green light. To design an effective model for a highly efficient InGaN green LEDs, this study considered the compositions of indium and aluminum for InxGal xN QW and AlyGal yN cap layers, along with different layer thicknesses of well, barrier and cap. These structural properties significantly affect different properties. For example, these properties affect electric fields of layers, polarization, overall elastic stress energy and lattice parameter of the structure, emission wavelength, and intensity of the emitted light. Three models with different composition and layer thicknesses are simulated and analyzed to obtain green light with in-plane equilibrium lattice parameter close to GaN (3.189 A ) with the highest oscillator strength values. A structure model is obtained with an oscillator strength value of 1.18 × 10-1 and least in-plane equilibrium lattice constant of 3.218 A. This emitter can emit at a wavelength of 540 nm, which is the expected design for the fabrication of highly efficient, bright green LEDs.
基金financially supported by the National Natural Science Foundation of China(NSFC:nos.51733010,51973239,and 52073316)the Guangdong Science and Technology Plan(nos.2015B090913003 and 2015B090915003).
文摘Hybridized local and charge-transfer(HLCT)excitedstate fluorophores,which enable full exciton utilization through a reverse intersystem crossing fromhigh-lying triplet states to singlet state,have attracted increasing attention toward organic light-emitting diodes(OLEDs)application.Herein,we report three D-π-A-π-D-type isomers o-2CzBT,m-2CzBT,and p-2CzBT by adjusting the donor(D)units from ortho-,meta-,to para-substituted positions with the acceptor(A)core unit,respectively.The HLCT properties of the three compounds are evidently confirmed by theoretical calculations,solvatochromic behaviors,and transient decay lifetimes analyses.As the substituted position changes from the ortho-,meta-,and para-positions,the reduced steric hindrance brings about decreased torsional angle between D and A moieties,resulting in increased oscillator strength.Accordingly,the parasubstituted p-2CzBT is endowed with a more locally excited component that accounts for faster radiative decay,leading to a higher fluorescent efficiency than that of o-2CzBT and m-2CzBT.As expected,p-2CzBT enables its nondoped and doped OLEDs with higher external quantum efficiencies(EQEs)of 12.3% and 15.0%,respectively,which are among the state-ofthe-art efficiencies of HLCT-based OLEDs.Moreover,o-2CzBT and m-2CzBT are also utilized as host materials for high-performance OLEDs,thus extending the application of HLCT materials.