Single(SA) and double(DA) Auger decay including cascade and direct processes are investigated for Hg 4 f^(-1) with multiconfiguration Dirac–Fock method and two-step approaches, i.e., knockout and shakeoff mecha...Single(SA) and double(DA) Auger decay including cascade and direct processes are investigated for Hg 4 f^(-1) with multiconfiguration Dirac–Fock method and two-step approaches, i.e., knockout and shakeoff mechanisms. Due to the computational effort, only the major transitions are considered to describe the SA and DA decays for the Hg+ions with complex electronic configurations. In order to estimate the Auger transition energies and amplitudes, the reference configuration sets producing the configuration state functions are carefully chosen for balancing electron correlations among the successive singly, doubly and triply ionized mercury. The Auger rates and electron spectra, DA probabilities as well as the populations of the final Hg^(3+)states are obtained. Our results well explain the recent experimental data about the 4 f hole states of Hg[Palaudoux J et al., Phys. Rev. A 91 012513(2015)], and could provide guidance for further studies on complex atoms.Particularly for the DA decay, the contributions of the direct processes, which are neglected in their calculations, are found to be important, accounting for as high as about 38% and 34% of the total DA decays for the 4 f(7/2)^(-1) and 4 f(5/2)^(-1), respectively.展开更多
The single-and double-electron capture(SEC, DEC) processes of He^(2+) ions colliding with Ne atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling method. Total and state-selectiv...The single-and double-electron capture(SEC, DEC) processes of He^(2+) ions colliding with Ne atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling method. Total and state-selective SEC and DEC cross sections are presented in the energy region of 2 eV/u to 20 keV/u. Results show that the dominant reaction channel is Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s) in the considered energy region due to strong couplings with the initial state Ne(2s^(2)2p^(6)^(1)S) + He^(2+) around the internuclear distance of 4.6 a.u. In our calculations, the SEC cross sections decrease initially and then increase whereby, the minimum point is around 0.38 keV/u with the increase of collision energies. After considering the effects of the electron translation factor(ETF), the SEC cross sections are increased by 15%–25% nearby the energy region of keV/u and agree better with the available results. The DEC cross sections are smaller than those of SEC because of the larger energy gaps and no strong couplings with the initial state. Due to the Demkov-type couplings between DEC channel Ne^(2+)(2s^(2)2p^(4)^(1)S) + He(1s^(2)) and the dominating SEC channel Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s), the DEC cross sections increase with increasing impact energies. Good consistency can also be found between the present DEC and the experimental measurements in the overlapping energy region.展开更多
Electron capture between solar wind ions and neutral species has contributed to the understanding of X-ray production from solar system bodies.The charge transfer and excitation processes in solar wind ions of He^(+)(...Electron capture between solar wind ions and neutral species has contributed to the understanding of X-ray production from solar system bodies.The charge transfer and excitation processes in solar wind ions of He^(+)(1 s) colliding with Li(1 s^(2)2 s) atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling(QMOCC) method with impact energies of 0.003-2 keV amu-1.Comparisons of cross sections from single-and multi-configurational calculations for a selfconsistent field(SCF and MCSCF) process are carried out.Results show that the dominant reaction channels are He(1 s2 l ^(1,3) L)+Li^(+)(1 s^(2) ^(1) S).Good consistency is found among present total and state-selective charge transfer and excitation cross sections with other theoretical and experimental data in the same energy region.Due to the differences between coupling matrix elements in high-energy states,the charge transfer cross sections calculated from SCF and MCSCF split slightly as E> 0.4 keV amu-1.Weak Stueckelberg oscillations for charge transfer appear in the present work.In addition,the differences of cross sections for electron excitation to Li(ls^(2)2 p) in the singlet/triplet molecular states with He+(1 s) are much smaller than those of charge transfer processes because of the similar energy gaps from Li(ls^(2)2 p) to the ground state in singlet/triplet states in the large R region.展开更多
The low-energy mutual neutralization(MN)reactions Na^(+)+H^(-)→Na(nl)+H have been studied by employing the full quantum-mechanical molecular-orbital close-coupling(QMOCC)method over a wide energy range of 10^(-3)-10^...The low-energy mutual neutralization(MN)reactions Na^(+)+H^(-)→Na(nl)+H have been studied by employing the full quantum-mechanical molecular-orbital close-coupling(QMOCC)method over a wide energy range of 10^(-3)-10^(3) e V/u.Total and state-selective cross sections have been investigated and compared with the available theoretical and experimental data,and the state-selective rate coefficients for the temperature range of 100-10000 K have been obtained.In the present work,all the necessary highly excited states are included,and the influences of rotational couplings and 10 active electrons are considered.It is found that in the energy below 10 e V/u,the Na(4s)state is the most dominant exit state with a contribution of approximately 78%to the branch fraction,which is in best agreement with the experimental data.For energies above 10 e V/u,the MN total cross section is larger than those obtained in other theoretical calculations and shows a slow decreasing trend because the main exit states change,when the energy is above 100 e V/u,the dominant exit state becomes the Na(3p)state,while the Na(4s)state becomes the third most important exit state.The datasets presented in this paper,including the potential energy curve,the radial and rotational couplings,the total and state-selective cross sections,are openly available at https://doi.org/10.57760/sciencedb.j00113.00112.展开更多
An 8×10 GHz receiver optical sub-assembly (ROSA) consisting of an 8-channel arrayed waveguide grating (AWG) and an 8-channel PIN photodetector (PD) array is designed and fabricated based on silica hybrid in...An 8×10 GHz receiver optical sub-assembly (ROSA) consisting of an 8-channel arrayed waveguide grating (AWG) and an 8-channel PIN photodetector (PD) array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain fiat-top spectra. The output waveguide facet is polished to 45° bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimentM results show that the single channel I dB bandwidth of AWG ranges from 2.12nm to 3.06nm, the ROSA responsivity ranges from 0.097 A/W to 0.158A/W, and the 3dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.展开更多
The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl '(n = 2,3,...,15) resonances.Then,the resonant tr...The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl '(n = 2,3,...,15) resonances.Then,the resonant transfer excitation(RTE) processes of Kr 34+ colliding with H,He,H 2,and CH x(x = 0-4) targets are investigated under the impulse approximation.The needed Compton profiles of targets are obtained from the Hartree-Fock wave functions.The RTE cross sections are strongly dependent on DR resonant energies and strengths,and the electron momentum distributions of the target.For H 2 and H targets,the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l ' to 1.88 for other resonances,which demonstrates the weak molecular effects on the Compton profiles of H 2.For CH x(x = 0-4) targets,the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons;as the number of hydrogen increases in CH x,the RTE cross section almost increases by the same value,displaying the strong separate atom character for the hydrogen.However,further comparison of the individual orbital contributions of C(2p,2s,1s) and CH 4(1t 2,2a 1,1a 1) to the RTE cross sections shows that the molecular effects induce differences of about 25.1%,19.9%,and 0.2% between 2p-1t 2,2s-2a 1,and 1s-1a 1 orbitals,respectively.展开更多
The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10-a keV-10 keV. Th...The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10-a keV-10 keV. The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region. The importance of rotational coupling for chargetransfer process is stressed. Compared with the radiative charge-transfer process, nonradiative charge transfer is a dominant mechanism at energies above 15 eV. The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail. The radiative and nonradiative1 charge-transfer rate coefficients from low to high temperature are presented.展开更多
The plasma screening of fast-electron-impact-ionization by excited state(3p) of Hydrogen-like ions was investigated in the first Born approximation with a plasma screening length δ varying from 1000a0 to 10a0. The ...The plasma screening of fast-electron-impact-ionization by excited state(3p) of Hydrogen-like ions was investigated in the first Born approximation with a plasma screening length δ varying from 1000a0 to 10a0. The generalized oscillator strength densities showed dramatic changes: some accessional minima occurred along with a remarkable enhancement in certain continuum-energy domains. The double-differential cross sections exhibit not only the same structures as the Bethe surface for moderate and large momentum transfers, but also a broadened enhancement for small momentum transfers.The single-differential cross sections exhibit a near-zero-energy-enhancement and prodigious multiple-shape resonances,depending on the continuum energy and the plasma screening length. These features are analogous to those of the photoionization cross section. These findings, for both types of cross section, can be explained by processes associated with continuum electrons, as long as the potential has a short-range character.展开更多
The 3s–np photoionization processes of the ground state 2P1/2 and the metastable state 2P3/2 of Ar5+ are investigated using our recently developed relativistic R-matrix code, where the interactions between the bound...The 3s–np photoionization processes of the ground state 2P1/2 and the metastable state 2P3/2 of Ar5+ are investigated using our recently developed relativistic R-matrix code, where the interactions between the bound states and the continuum states are included. Both resonance positions and the oscillator strengths are in much better agreement with the absolute experimental measurements by Wang et al.[Wang J C, Lu M, Esteves D, Habibi M, Alna’washi G and Phaneuf R A 2007 Phys. Rev. A 75 062712] with a resolution of 80 meV than their theoretical results. The contributions of the two experimental unresolved transitions are distinguished in our calculations, which show that the transitions from the ground state also make significant contributions to some resonances. Our theoretical results are also in good agreement with the measurements for the first resonance with a higher resolution of 20 meV.展开更多
We study the relationship between electromagnetically-induced transparency(EIT) and Autler–Townes(AT) splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the flu...We study the relationship between electromagnetically-induced transparency(EIT) and Autler–Townes(AT) splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the fluorescence excitation spectrum, it is found that for a Doppler-broadened system, EIT resonance cannot be explained as the result of quantum interference, unlike the case of a homogeneously broadened system. Instead, the macroscopic polarization interference plays an important role in determining the spectra of EIT and AT splitting, which can be explained within the same framework when being detected by the absorption spectra.展开更多
We measure the absorption and dispersion in a Doppler-broadened A-type three level system by resonant stimulated Raman spectroscopy with homodyne detection. Through studying the dressed state energies of the system, i...We measure the absorption and dispersion in a Doppler-broadened A-type three level system by resonant stimulated Raman spectroscopy with homodyne detection. Through studying the dressed state energies of the system, it is found that the absorption and dispersion satisfy the Kramers-Kronig relation. The absorption and dispersion spectra calculated by employing this relation agree well with our experimental observations.展开更多
The resonant charge transfer process for Li+-Li(2s) collision is investigated by the quantum-mechanical molecular orbital close-coupling(QMOCC) method and the two-center atomic-orbital close-coupling(AOCC) meth...The resonant charge transfer process for Li+-Li(2s) collision is investigated by the quantum-mechanical molecular orbital close-coupling(QMOCC) method and the two-center atomic-orbital close-coupling(AOCC) method in an energy range of 1.0 e V/u-104e V/u. Accurate molecular structure data and charge transfer cross sections are given. Both the allelectron model(AEM) and one-electron model(OEM) are used in the QMOCC calculations, and the discrepancies between the two models are analyzed. The OEM calculation can also give a reliable prediction of the cross sections for energies below 1 ke V/u.展开更多
We study the electromagnetically-induced transparency(EIT) in a Doppler-broadened cascaded three-level system.We decompose the susceptibility responsible for the EIT resonance into a linear and a nonlinear part, and...We study the electromagnetically-induced transparency(EIT) in a Doppler-broadened cascaded three-level system.We decompose the susceptibility responsible for the EIT resonance into a linear and a nonlinear part, and the EIT resonance reflects mainly the characteristics of the nonlinear susceptibility. It is found that the macroscopic polarization interference effect plays a crucial role in determining the EIT resonance spectrum. To obtain a Doppler-free spectrum there must be polarization interference between atoms of different velocities. A dressed-state model, which analyzes the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting, is employed to explain the results.展开更多
The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl ’(n = 2,3,...,15) resonances.Then,the resonant transf...The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl ’(n = 2,3,...,15) resonances.Then,the resonant transfer excitation(RTE) processes of Kr 34+ colliding with H,He,H 2,and CH x(x = 0-4) targets are investigated under the impulse approximation.The needed Compton profiles of targets are obtained from the Hartree-Fock wave functions.The RTE cross sections are strongly dependent on DR resonant energies and strengths,and the electron momentum distributions of the target.For H 2 and H targets,the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l ’ to 1.88 for other resonances,which demonstrates the weak molecular effects on the Compton profiles of H 2.For CH x(x = 0-4) targets,the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons;as the number of hydrogen increases in CH x,the RTE cross section almost increases by the same value,displaying the strong separate atom character for the hydrogen.However,further comparison of the individual orbital contributions of C(2p,2s,1s) and CH 4(1t 2,2a 1,1a 1) to the RTE cross sections shows that the molecular effects induce differences of about 25.1%,19.9%,and 0.2% between 2p-1t 2,2s-2a 1,and 1s-1a 1 orbitals,respectively.展开更多
A 1 550 nm long-wavelength vertical cavity surface emitting laser(VCSEL)on InP substrate is designed and fabr icated.The transfer matrix is used to compute reflectivity spectrum of the designed epitaxial layers.The ep...A 1 550 nm long-wavelength vertical cavity surface emitting laser(VCSEL)on InP substrate is designed and fabr icated.The transfer matrix is used to compute reflectivity spectrum of the designed epitaxial layers.The epitaxial layers mainly consist of 40 pairs of n-Al_(x )Ga_(y )In_((1-x-y))As/InP,and 6 strain compensated Al_(x )Ga_(y )In_((1-x-y))As/InP quantum wells on n-InP substrate,respectively.The top distributed Bragg reflection(DBR)mirror system has been formed by fabricating 4.5 pairs of SiO_2/Si.The designed cavity mode is around 1 536 nm.The dip of the fabricated cavity mode is around 1 530 nm.The threshold current is 30 mA and the maximum output power is around 270μW under CW operation at room temperature.展开更多
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)+1 种基金the Joint Foundation of the National Natural Science Foundationthe China Academy of Engineering Physics(Grant No.U1330117)
文摘Single(SA) and double(DA) Auger decay including cascade and direct processes are investigated for Hg 4 f^(-1) with multiconfiguration Dirac–Fock method and two-step approaches, i.e., knockout and shakeoff mechanisms. Due to the computational effort, only the major transitions are considered to describe the SA and DA decays for the Hg+ions with complex electronic configurations. In order to estimate the Auger transition energies and amplitudes, the reference configuration sets producing the configuration state functions are carefully chosen for balancing electron correlations among the successive singly, doubly and triply ionized mercury. The Auger rates and electron spectra, DA probabilities as well as the populations of the final Hg^(3+)states are obtained. Our results well explain the recent experimental data about the 4 f hole states of Hg[Palaudoux J et al., Phys. Rev. A 91 012513(2015)], and could provide guidance for further studies on complex atoms.Particularly for the DA decay, the contributions of the direct processes, which are neglected in their calculations, are found to be important, accounting for as high as about 38% and 34% of the total DA decays for the 4 f(7/2)^(-1) and 4 f(5/2)^(-1), respectively.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 11774344 and 11474033)the National Key Research and Development Program of China (Grant No. 2017YFA0402300)。
文摘The single-and double-electron capture(SEC, DEC) processes of He^(2+) ions colliding with Ne atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling method. Total and state-selective SEC and DEC cross sections are presented in the energy region of 2 eV/u to 20 keV/u. Results show that the dominant reaction channel is Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s) in the considered energy region due to strong couplings with the initial state Ne(2s^(2)2p^(6)^(1)S) + He^(2+) around the internuclear distance of 4.6 a.u. In our calculations, the SEC cross sections decrease initially and then increase whereby, the minimum point is around 0.38 keV/u with the increase of collision energies. After considering the effects of the electron translation factor(ETF), the SEC cross sections are increased by 15%–25% nearby the energy region of keV/u and agree better with the available results. The DEC cross sections are smaller than those of SEC because of the larger energy gaps and no strong couplings with the initial state. Due to the Demkov-type couplings between DEC channel Ne^(2+)(2s^(2)2p^(4)^(1)S) + He(1s^(2)) and the dominating SEC channel Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s), the DEC cross sections increase with increasing impact energies. Good consistency can also be found between the present DEC and the experimental measurements in the overlapping energy region.
基金supported by the National Natural Science Foundation of China (Grant Nos.11774344,11474033 and 11574326)the National Key Research and Development Program of China (Grant No.2017YFA0402300)。
文摘Electron capture between solar wind ions and neutral species has contributed to the understanding of X-ray production from solar system bodies.The charge transfer and excitation processes in solar wind ions of He^(+)(1 s) colliding with Li(1 s^(2)2 s) atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling(QMOCC) method with impact energies of 0.003-2 keV amu-1.Comparisons of cross sections from single-and multi-configurational calculations for a selfconsistent field(SCF and MCSCF) process are carried out.Results show that the dominant reaction channels are He(1 s2 l ^(1,3) L)+Li^(+)(1 s^(2) ^(1) S).Good consistency is found among present total and state-selective charge transfer and excitation cross sections with other theoretical and experimental data in the same energy region.Due to the differences between coupling matrix elements in high-energy states,the charge transfer cross sections calculated from SCF and MCSCF split slightly as E> 0.4 keV amu-1.Weak Stueckelberg oscillations for charge transfer appear in the present work.In addition,the differences of cross sections for electron excitation to Li(ls^(2)2 p) in the singlet/triplet molecular states with He+(1 s) are much smaller than those of charge transfer processes because of the similar energy gaps from Li(ls^(2)2 p) to the ground state in singlet/triplet states in the large R region.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12204288,11934004,and 12203106)。
文摘The low-energy mutual neutralization(MN)reactions Na^(+)+H^(-)→Na(nl)+H have been studied by employing the full quantum-mechanical molecular-orbital close-coupling(QMOCC)method over a wide energy range of 10^(-3)-10^(3) e V/u.Total and state-selective cross sections have been investigated and compared with the available theoretical and experimental data,and the state-selective rate coefficients for the temperature range of 100-10000 K have been obtained.In the present work,all the necessary highly excited states are included,and the influences of rotational couplings and 10 active electrons are considered.It is found that in the energy below 10 e V/u,the Na(4s)state is the most dominant exit state with a contribution of approximately 78%to the branch fraction,which is in best agreement with the experimental data.For energies above 10 e V/u,the MN total cross section is larger than those obtained in other theoretical calculations and shows a slow decreasing trend because the main exit states change,when the energy is above 100 e V/u,the dominant exit state becomes the Na(3p)state,while the Na(4s)state becomes the third most important exit state.The datasets presented in this paper,including the potential energy curve,the radial and rotational couplings,the total and state-selective cross sections,are openly available at https://doi.org/10.57760/sciencedb.j00113.00112.
基金Supported by the National High Technology Research and Development Program of China under Grant No 2015AA016902the National Natural Science Foundation of China under Grant Nos 61435013 and 61405188the K.C.Wong Education Foundation
文摘An 8×10 GHz receiver optical sub-assembly (ROSA) consisting of an 8-channel arrayed waveguide grating (AWG) and an 8-channel PIN photodetector (PD) array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain fiat-top spectra. The output waveguide facet is polished to 45° bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimentM results show that the single channel I dB bandwidth of AWG ranges from 2.12nm to 3.06nm, the ROSA responsivity ranges from 0.097 A/W to 0.158A/W, and the 3dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10876043, 10774186 and 10734040, and the National Key Laboratory of Computational Physics Foundation under Grant No 9140C6904030808.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 1179041,11025417,and 10979007) the NSAF (Grant No. 10876043)
文摘The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl '(n = 2,3,...,15) resonances.Then,the resonant transfer excitation(RTE) processes of Kr 34+ colliding with H,He,H 2,and CH x(x = 0-4) targets are investigated under the impulse approximation.The needed Compton profiles of targets are obtained from the Hartree-Fock wave functions.The RTE cross sections are strongly dependent on DR resonant energies and strengths,and the electron momentum distributions of the target.For H 2 and H targets,the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l ' to 1.88 for other resonances,which demonstrates the weak molecular effects on the Compton profiles of H 2.For CH x(x = 0-4) targets,the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons;as the number of hydrogen increases in CH x,the RTE cross section almost increases by the same value,displaying the strong separate atom character for the hydrogen.However,further comparison of the individual orbital contributions of C(2p,2s,1s) and CH 4(1t 2,2a 1,1a 1) to the RTE cross sections shows that the molecular effects induce differences of about 25.1%,19.9%,and 0.2% between 2p-1t 2,2s-2a 1,and 1s-1a 1 orbitals,respectively.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10979007,11025417,11179041,and 11004014)the NSAF (Grant No. 10876043)
文摘The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10-a keV-10 keV. The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region. The importance of rotational coupling for chargetransfer process is stressed. Compared with the radiative charge-transfer process, nonradiative charge transfer is a dominant mechanism at energies above 15 eV. The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail. The radiative and nonradiative1 charge-transfer rate coefficients from low to high temperature are presented.
基金supported by the National Basic Research Program of China(Grant No.2013CB922200)the National Natural Science Foundation of China(Grant Nos.11005049,11025417,and 10974021)
文摘The plasma screening of fast-electron-impact-ionization by excited state(3p) of Hydrogen-like ions was investigated in the first Born approximation with a plasma screening length δ varying from 1000a0 to 10a0. The generalized oscillator strength densities showed dramatic changes: some accessional minima occurred along with a remarkable enhancement in certain continuum-energy domains. The double-differential cross sections exhibit not only the same structures as the Bethe surface for moderate and large momentum transfers, but also a broadened enhancement for small momentum transfers.The single-differential cross sections exhibit a near-zero-energy-enhancement and prodigious multiple-shape resonances,depending on the continuum energy and the plasma screening length. These features are analogous to those of the photoionization cross section. These findings, for both types of cross section, can be explained by processes associated with continuum electrons, as long as the potential has a short-range character.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11179041 and 11275029)
文摘The 3s–np photoionization processes of the ground state 2P1/2 and the metastable state 2P3/2 of Ar5+ are investigated using our recently developed relativistic R-matrix code, where the interactions between the bound states and the continuum states are included. Both resonance positions and the oscillator strengths are in much better agreement with the absolute experimental measurements by Wang et al.[Wang J C, Lu M, Esteves D, Habibi M, Alna’washi G and Phaneuf R A 2007 Phys. Rev. A 75 062712] with a resolution of 80 meV than their theoretical results. The contributions of the two experimental unresolved transitions are distinguished in our calculations, which show that the transitions from the ground state also make significant contributions to some resonances. Our theoretical results are also in good agreement with the measurements for the first resonance with a higher resolution of 20 meV.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404330,11274376,61308011,and 11474347)the NSAF,China(Grant No.U1330117)+1 种基金the National Basic Research Program of China(Grant Nos.2013CB922002 and 2010CB922904)the China Postdoctoral Science Foundation(Grant No.119103S239)
文摘We study the relationship between electromagnetically-induced transparency(EIT) and Autler–Townes(AT) splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the fluorescence excitation spectrum, it is found that for a Doppler-broadened system, EIT resonance cannot be explained as the result of quantum interference, unlike the case of a homogeneously broadened system. Instead, the macroscopic polarization interference plays an important role in determining the spectra of EIT and AT splitting, which can be explained within the same framework when being detected by the absorption spectra.
基金supported by the National Basic Research Program of China(Grant Nos.2013CB922002 and 2010CB922904)the National Natural Science Foundation of China(Grant Nos.11274376 and 61308011)the Natural Science Foundation of Hebei Province,China(Grant No.A2015205161)
文摘We measure the absorption and dispersion in a Doppler-broadened A-type three level system by resonant stimulated Raman spectroscopy with homodyne detection. Through studying the dressed state energies of the system, it is found that the absorption and dispersion satisfy the Kramers-Kronig relation. The absorption and dispersion spectra calculated by employing this relation agree well with our experimental observations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11179041,11474032,and 11474033)the NSAF(Grant No.U1330117)
文摘The resonant charge transfer process for Li+-Li(2s) collision is investigated by the quantum-mechanical molecular orbital close-coupling(QMOCC) method and the two-center atomic-orbital close-coupling(AOCC) method in an energy range of 1.0 e V/u-104e V/u. Accurate molecular structure data and charge transfer cross sections are given. Both the allelectron model(AEM) and one-electron model(OEM) are used in the QMOCC calculations, and the discrepancies between the two models are analyzed. The OEM calculation can also give a reliable prediction of the cross sections for energies below 1 ke V/u.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10974252,11274376,60978002,and 11179041)the National Basic Research Program of China(Grant No.2010CB922904)+2 种基金the National High Technology Research and Development Program of China(Grant No.2011AA120102)the Natural Science Foundation of Inner Mongolia,China(Grants No.2012MS0101)the Innovation Fund of Inner Mongolia University of Science and Technology,China(Grants No.2010NC064)
文摘We study the electromagnetically-induced transparency(EIT) in a Doppler-broadened cascaded three-level system.We decompose the susceptibility responsible for the EIT resonance into a linear and a nonlinear part, and the EIT resonance reflects mainly the characteristics of the nonlinear susceptibility. It is found that the macroscopic polarization interference effect plays a crucial role in determining the EIT resonance spectrum. To obtain a Doppler-free spectrum there must be polarization interference between atoms of different velocities. A dressed-state model, which analyzes the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting, is employed to explain the results.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 1179041,11025417,and 10979007)the NSAF (Grant No. 10876043)
文摘The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl ’(n = 2,3,...,15) resonances.Then,the resonant transfer excitation(RTE) processes of Kr 34+ colliding with H,He,H 2,and CH x(x = 0-4) targets are investigated under the impulse approximation.The needed Compton profiles of targets are obtained from the Hartree-Fock wave functions.The RTE cross sections are strongly dependent on DR resonant energies and strengths,and the electron momentum distributions of the target.For H 2 and H targets,the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l ’ to 1.88 for other resonances,which demonstrates the weak molecular effects on the Compton profiles of H 2.For CH x(x = 0-4) targets,the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons;as the number of hydrogen increases in CH x,the RTE cross section almost increases by the same value,displaying the strong separate atom character for the hydrogen.However,further comparison of the individual orbital contributions of C(2p,2s,1s) and CH 4(1t 2,2a 1,1a 1) to the RTE cross sections shows that the molecular effects induce differences of about 25.1%,19.9%,and 0.2% between 2p-1t 2,2s-2a 1,and 1s-1a 1 orbitals,respectively.
基金supported by the National High Technology and Development Program of China(No.2015AA016902)
文摘A 1 550 nm long-wavelength vertical cavity surface emitting laser(VCSEL)on InP substrate is designed and fabr icated.The transfer matrix is used to compute reflectivity spectrum of the designed epitaxial layers.The epitaxial layers mainly consist of 40 pairs of n-Al_(x )Ga_(y )In_((1-x-y))As/InP,and 6 strain compensated Al_(x )Ga_(y )In_((1-x-y))As/InP quantum wells on n-InP substrate,respectively.The top distributed Bragg reflection(DBR)mirror system has been formed by fabricating 4.5 pairs of SiO_2/Si.The designed cavity mode is around 1 536 nm.The dip of the fabricated cavity mode is around 1 530 nm.The threshold current is 30 mA and the maximum output power is around 270μW under CW operation at room temperature.