Using the closed orbit theory, we study the classical motion and calculatethe photoabsorption spectra of Rydberg hydrogen atom between two parallel metallic surfaces. The results show that the metallic surfaces have a...Using the closed orbit theory, we study the classical motion and calculatethe photoabsorption spectra of Rydberg hydrogen atom between two parallel metallic surfaces. The results show that the metallic surfaces have a significant effect on the photoabsorption process. When the distances between the hydrogen atom and the two metallic surfaces are close to a critical value dc, the number of the closed orbits is the greatest. When the distance larger or smaller than dc, the number of the closed orbits decreases and the absorption spectra are shown to exhibit a damping oscillation. This work is an interesting new application of closed-orbit theory and is of potential experimental interest.展开更多
The photoabsorption cross sections of condensed atoms and molecules have proven to be dependent not only on the imaginary parts but also on the real parts of the polarizabilities due to the strong interatomie interact...The photoabsorption cross sections of condensed atoms and molecules have proven to be dependent not only on the imaginary parts but also on the real parts of the polarizabilities due to the strong interatomie interactions in condensed environment. The real parts of the polarizabilities calculated usually by using the famous Kramers-Kronig transformation （KKT） from the photoabsorption cross sections of the isolated atoms are very sensitive to the accuracy of the implementation method of the infinite integral in the KKT. The influence of the integral instability of the KKT and the real part of the polarizability on the variation of the photoabsorption cross sections with the number density and the structure of the condensed matter has been studied in the present work for the first time. The conclusion is that the integration method with interpolation has given more reasonable results than the direct truncation method if some appropriate interpolation functions have been used. Some notes and conclusions have also been given for the applications of the alternative coupled expressions of photoabsorption cross sections.展开更多
The photosensitivity of silicon is inherently very low in the visible electromagnetic spectrum,and it drops rapidly beyond 800 nm in near-infrared wavelengths.We have experimentally demonstrated a technique utilizing ...The photosensitivity of silicon is inherently very low in the visible electromagnetic spectrum,and it drops rapidly beyond 800 nm in near-infrared wavelengths.We have experimentally demonstrated a technique utilizing photon-trapping surface structures to show a prodigious improvement of photoabsorption in 1-μm-thin silicon,surpassing the inherent absorption efficiency of gallium arsenide for a broad spectrum.The photon-trapping structures allow the bending of normally incident light by almost 90 deg to transform into laterally propagating modes along the silicon plane.Consequently,the propagation length of light increases,contributing to more than one order of magnitude improvement in absorption efficiency in photodetectors.This high-absorption phenomenon is explained by finitedifference time-domain analysis,where we show an enhanced photon density of states while substantially reducing the optical group velocity of light compared to silicon without photon-trapping structures,leading to significantly enhanced light–matter interactions.Our simulations also predict an enhanced absorption efficiency of photodetectors designed using 30-and 100-nm silicon thin films that are compatible with CMOS electronics.Despite a very thin absorption layer,such photon-trapping structures can enable high-efficiency and high-speed photodetectors needed in ultrafast computer networks,data communication,and imaging systems,with the potential to revolutionize on-chip logic and optoelectronic integration.展开更多
The photoabsorption spectra have been calculated for Sis and SilO （n ≤ 5） clusters using time-dependent density-function theory. Our studies suggest that Sin-1 O clusters are relatively stable than those of corresp...The photoabsorption spectra have been calculated for Sis and SilO （n ≤ 5） clusters using time-dependent density-function theory. Our studies suggest that Sin-1 O clusters are relatively stable than those of corresponding Sis clusters. Moreover, substantial differences are observed among the absorption spectra of different molecules in the energy region （0 - 8 eV）. Comparing two different exchange-correlation potentials, local-density and generalized-gradient approximations, both calculated optical spectra present the same spectral feature.展开更多
The influence of the local-field on the photoabsorption cross section of the atomic silver is studied in detail by using the Clausius-Mossotti （CM） model and the Onsager model separately. The variations of the photo...The influence of the local-field on the photoabsorption cross section of the atomic silver is studied in detail by using the Clausius-Mossotti （CM） model and the Onsager model separately. The variations of the photoabsorption cross section of atomic silver with number density and radius of the environmental interaction cavity are studied systematically by using more general expressions for the photoabsorption cross sections, proposed by Sun et al recently. It has proved to be reasonable to model the optical response properties of bulky material by coupling the property of isolated atom with the environmental effects in the present work.展开更多
The evolution of the photoabsorption cross sections of atomic xenon with number densities varying from ideal gas to condensed matter has been studied by an alternative view in the present work. The alternative express...The evolution of the photoabsorption cross sections of atomic xenon with number densities varying from ideal gas to condensed matter has been studied by an alternative view in the present work. The alternative expressions of the photoabsorption cross sections presented by Sun et al recently were used with the local field models that has proven to be generalized easily to multiatoinic systems including molecules and condensed phase systems. The present results show that the variation of the photoabsorption cross sections of atomic xenon in the giant resonance region from the isolated to the condensed conditions is very small, which agrees well with the variation law of the solid and gas experiments.展开更多
The strong interatomic interaction effects on photoabsorption cross sections of a private atom have been interpreted by the contribution of both the real and imaginary parts of atomic polarizability in the present wor...The strong interatomic interaction effects on photoabsorption cross sections of a private atom have been interpreted by the contribution of both the real and imaginary parts of atomic polarizability in the present work. Some unresolved differences between the photoabsorption cross sections of isolated atoms and those of condensed atoms, especially near thresholds and resonances, probably could be interpreted by the competition between the imaginary and real parts of atomic frequency-dependent polarizabilities.展开更多
We apply the B3LYP, PBE1PBE and B3PW91 methods of density functional theory and time-dependent density functional theory within the local density approximation to the description of structures and photoabsorption spec...We apply the B3LYP, PBE1PBE and B3PW91 methods of density functional theory and time-dependent density functional theory within the local density approximation to the description of structures and photoabsorption spectra of B10 and B10. Several other properties, such as relative energies, average binding energies, average B-B bond lengths, have been also investigated. It is found that the ground state of B10 is quasi-planar structure with C2h symmetry, while the lowest energy state of B10 anion is quasi-planar structure with C1 symmetry. The average B-B bond lengths of the anion are very close to that of the corresponding neutral clusters. Substantial differences of photoabsorption spectra are observed between different isomers which can be used for comparison against future experimental investigations. And the spectra for the anionic clusters display a red shift with respect to the spectra of their corresponding neutral clusters.展开更多
Based on multi-scattering self-consistent field method, the photoabsorption spectra near C 1s threshold of CH4(near-threshold structure) have been studied with the broken symmetry from Td. The most possible geometry o...Based on multi-scattering self-consistent field method, the photoabsorption spectra near C 1s threshold of CH4(near-threshold structure) have been studied with the broken symmetry from Td. The most possible geometry of the core excited CH4** is determined as the C3v symmetry; the core excited CH4** molecules have the same bond angle (109.5? as that of the ground state CH4 and consist of one shorter bond length (1.91 a. u.) and three longer bond lengths (2.04 a. u.). The three longer bond lengths are almost the same as that of the ground state CH4, and the averaged bond length (2.01 a.u.) of core excited CH4** is shorter than that of the ground state CH4(2.06 a.u.).展开更多
Photoionization can generally be decomposed into a photoabsorption process plus a half-scattering process.The streaking time delay observed in the attosecond streak camera,correspondingly,can be decomposed into a phot...Photoionization can generally be decomposed into a photoabsorption process plus a half-scattering process.The streaking time delay observed in the attosecond streak camera,correspondingly,can be decomposed into a photoabsorption time delay and a continuum time delay.We propose a self-consistent method to account for the potential-laser coupling effect and extract the intrinsic absorption time delay,without invoking an implicit assumption of a constant continuum correction made in previous streaking studies.The concept is based on an iterative technique starting from an initial guess of the absorption time delay and using classical electron trajectories to consistently remove the coupling-induced momentum shift to the streak signal.We show that the self-consistent iterative algorithm converges quickly and is robust against different initial guesses.The method is applied to laser-induced ionization of atoms to obtain the absorption time delay in resonant two-photon ionization and to explore possible time delays in above-threshold ionization.The results confirm an absorption time delay linearly dependent on the ionizing pulse duration in resonant two-photon ionization.The method is also shown to perform better than conventional methods and to identify a small negative absorption time delay(less than 2 attoseconds) in above-threshold ionization.展开更多
In the framework of quantum defect theory, we study super-excited states of F2 molecules which can dissociate into F^＋ （^3P2,1,0） and F^-（^1 So） ion-pair. Based on our calculation, we present a vibrational resolv...In the framework of quantum defect theory, we study super-excited states of F2 molecules which can dissociate into F^＋ （^3P2,1,0） and F^-（^1 So） ion-pair. Based on our calculation, we present a vibrational resolved assignment of the high precision photofragment yield spectra for F^- from the F2 ion-pair production.展开更多
Valence band photoemission spectra (PES) for both bulk and nanocrystal CeO2 have been measured on and off resonance of Ce 4d-4f absorption edge. The PES show that the bulk and nanocrystal CeO2 of diameter ranging from...Valence band photoemission spectra (PES) for both bulk and nanocrystal CeO2 have been measured on and off resonance of Ce 4d-4f absorption edge. The PES show that the bulk and nanocrystal CeO2 of diameter ranging from 8nm to 50nm exhibit a peak near Fermi edge with binding energy of about 1.8eV. The 1.8eV peak shows a strong dependence on excitation energy, although it looks like the contribution of Ce3+ ion following the data reported in literatures. However, according to the results of resonance photoemission and X-ray absorption spectra at 1s edge, this electronic structure may be associated to the intermediate state charge transfer effects.展开更多
In the present paper, the time-resolved transient absorption spectroscopy of helium atoms is investigated based on the three-level modeling. The helium atoms are subjected to an extreme ultraviolet （XUV） attosecond ...In the present paper, the time-resolved transient absorption spectroscopy of helium atoms is investigated based on the three-level modeling. The helium atoms are subjected to an extreme ultraviolet （XUV） attosecond pulse and a time-delayed infrared （IR） few-cycle laser field. The odd excited state are populated from the ground state by the XUV pulse due to the dipole selection rule, and probed by the time-delayed IR laser. The time-resolved transient absorption spectroscopy based on the different coupling mechanism demonstrate some different features, the photoabsorption spectrum based on three-level model with rotating wave approximation （RWA） cannot repeat the fast oscillation and the sideband structure which have been observed in the previous experimental investigation. The dressing effect of IR laser pulse on the ground state can contribute new interference structures in the photoabsorption spectrum.展开更多
This work reports pressure-broadening line-wing and line-core of the lithium Li(2p←2s)resonance line perturbed by ground sodium Na(3s)atoms.In far-wing regions,the calculations are performed quantum-mechanically and ...This work reports pressure-broadening line-wing and line-core of the lithium Li(2p←2s)resonance line perturbed by ground sodium Na(3s)atoms.In far-wing regions,the calculations are performed quantum-mechanically and are intended to examine the photoabsorption coefficients at diverse temperatures.The results show the existence of three satellites,in the blue wing near the wavelengths 470 nm and in the red wing around 862 nm and 1070 nm.For the line-core region,by adopting the simplified Baranger model,the line-width and line-shift rates are determined,and their variation law with temperature is examined.No published data were found to compare these results with.展开更多
In nuclear ab initio calculations,nucleon-nucleon interactions are softened via renormalization in order to improve the convergence of calculations.The high-momentum and high-excitation properties of nuclei are not we...In nuclear ab initio calculations,nucleon-nucleon interactions are softened via renormalization in order to improve the convergence of calculations.The high-momentum and high-excitation properties of nuclei are not well investigated quantitatively with softened interactions to identify where they may lose predictive power though the low energy observables remain nearly unchanged after the renormalization.In this work,we study nuclear high-mo-mentum properties and high-excitation properties with realistic interactions taking the simplest nucleus,i.e.,deuter-on,as an example.In particular,we study the nucleon momentum distribution and photoabsorption cross section with a chiral effective field theory interaction at N^(3)LO and two softened interactions based on it,i.e.,N^(3)LO-SRG and Daejeon16 interactions.We find that the nucleon momentum distributions of the deuteron calculated with these two soft interactions are significantly suppressed at momenta above 200 MeV in comparison to those calculated with the N^(3)LO chiral interaction.The photoabsorption cross sections of the deuteron calculated with these three interac-tions are overall in agreement with the experimental data.The N^(3)LO-SRG results deviate slightly from the experi-mental data above about 15 MeV due to the renormalization process.The Daejeon16 results deviate more apparently from the experimental data above the peak value compared to the N^(3)LO-SRG results due to the phase equivalent transformations.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10604045） and the Doctorate Research Foundation of Ludong University, China （Grant No 202-23000301）.
文摘Using the closed orbit theory, we study the classical motion and calculatethe photoabsorption spectra of Rydberg hydrogen atom between two parallel metallic surfaces. The results show that the metallic surfaces have a significant effect on the photoabsorption process. When the distances between the hydrogen atom and the two metallic surfaces are close to a critical value dc, the number of the closed orbits is the greatest. When the distance larger or smaller than dc, the number of the closed orbits decreases and the absorption spectra are shown to exhibit a damping oscillation. This work is an interesting new application of closed-orbit theory and is of potential experimental interest.
基金Supported by the Natural Science Foundations of Ludong University under Grant Nos.22270301 and L20072804
文摘The photoabsorption cross sections of condensed atoms and molecules have proven to be dependent not only on the imaginary parts but also on the real parts of the polarizabilities due to the strong interatomie interactions in condensed environment. The real parts of the polarizabilities calculated usually by using the famous Kramers-Kronig transformation （KKT） from the photoabsorption cross sections of the isolated atoms are very sensitive to the accuracy of the implementation method of the infinite integral in the KKT. The influence of the integral instability of the KKT and the real part of the polarizability on the variation of the photoabsorption cross sections with the number density and the structure of the condensed matter has been studied in the present work for the first time. The conclusion is that the integration method with interpolation has given more reasonable results than the direct truncation method if some appropriate interpolation functions have been used. Some notes and conclusions have also been given for the applications of the alternative coupled expressions of photoabsorption cross sections.
基金supported in part by the US Army’s Night Vision and Electronic Sensors Directorate(Grant No.W909MY-12-D-0008)NSF ECCS(Grant No.1428392)。
文摘The photosensitivity of silicon is inherently very low in the visible electromagnetic spectrum,and it drops rapidly beyond 800 nm in near-infrared wavelengths.We have experimentally demonstrated a technique utilizing photon-trapping surface structures to show a prodigious improvement of photoabsorption in 1-μm-thin silicon,surpassing the inherent absorption efficiency of gallium arsenide for a broad spectrum.The photon-trapping structures allow the bending of normally incident light by almost 90 deg to transform into laterally propagating modes along the silicon plane.Consequently,the propagation length of light increases,contributing to more than one order of magnitude improvement in absorption efficiency in photodetectors.This high-absorption phenomenon is explained by finitedifference time-domain analysis,where we show an enhanced photon density of states while substantially reducing the optical group velocity of light compared to silicon without photon-trapping structures,leading to significantly enhanced light–matter interactions.Our simulations also predict an enhanced absorption efficiency of photodetectors designed using 30-and 100-nm silicon thin films that are compatible with CMOS electronics.Despite a very thin absorption layer,such photon-trapping structures can enable high-efficiency and high-speed photodetectors needed in ultrafast computer networks,data communication,and imaging systems,with the potential to revolutionize on-chip logic and optoelectronic integration.
基金supported by the National Natural Science Foundation of China and China Academy of Engineering Physics under Grant No. 10676025 (NSAF)
文摘The photoabsorption spectra have been calculated for Sis and SilO （n ≤ 5） clusters using time-dependent density-function theory. Our studies suggest that Sin-1 O clusters are relatively stable than those of corresponding Sis clusters. Moreover, substantial differences are observed among the absorption spectra of different molecules in the energy region （0 - 8 eV）. Comparing two different exchange-correlation potentials, local-density and generalized-gradient approximations, both calculated optical spectra present the same spectral feature.
基金Project supported by the Natural Science Foundation of Ludong University, China (Grant Nos 22270301 and L20072804)
文摘The influence of the local-field on the photoabsorption cross section of the atomic silver is studied in detail by using the Clausius-Mossotti （CM） model and the Onsager model separately. The variations of the photoabsorption cross section of atomic silver with number density and radius of the environmental interaction cavity are studied systematically by using more general expressions for the photoabsorption cross sections, proposed by Sun et al recently. It has proved to be reasonable to model the optical response properties of bulky material by coupling the property of isolated atom with the environmental effects in the present work.
基金Project supported by the Natural Science Foundations of Ludong University,Shandong Province,China (Grant Nos 22270301 and L20072804)
文摘The evolution of the photoabsorption cross sections of atomic xenon with number densities varying from ideal gas to condensed matter has been studied by an alternative view in the present work. The alternative expressions of the photoabsorption cross sections presented by Sun et al recently were used with the local field models that has proven to be generalized easily to multiatoinic systems including molecules and condensed phase systems. The present results show that the variation of the photoabsorption cross sections of atomic xenon in the giant resonance region from the isolated to the condensed conditions is very small, which agrees well with the variation law of the solid and gas experiments.
基金Project partly supported by the University Science & Technology Planning Program of Shandong Province of China (Grant No. J10LB60)Discipline Construction Fund and 2009 Technology Innovation Fund of Ludong University (Grant No. 09L026)
文摘The strong interatomic interaction effects on photoabsorption cross sections of a private atom have been interpreted by the contribution of both the real and imaginary parts of atomic polarizability in the present work. Some unresolved differences between the photoabsorption cross sections of isolated atoms and those of condensed atoms, especially near thresholds and resonances, probably could be interpreted by the competition between the imaginary and real parts of atomic frequency-dependent polarizabilities.
基金Supported by the National Natural Science Foundation of China and China Academy of Engineering Physics(No.10676025)
文摘We apply the B3LYP, PBE1PBE and B3PW91 methods of density functional theory and time-dependent density functional theory within the local density approximation to the description of structures and photoabsorption spectra of B10 and B10. Several other properties, such as relative energies, average binding energies, average B-B bond lengths, have been also investigated. It is found that the ground state of B10 is quasi-planar structure with C2h symmetry, while the lowest energy state of B10 anion is quasi-planar structure with C1 symmetry. The average B-B bond lengths of the anion are very close to that of the corresponding neutral clusters. Substantial differences of photoabsorption spectra are observed between different isomers which can be used for comparison against future experimental investigations. And the spectra for the anionic clusters display a red shift with respect to the spectra of their corresponding neutral clusters.
文摘Based on multi-scattering self-consistent field method, the photoabsorption spectra near C 1s threshold of CH4(near-threshold structure) have been studied with the broken symmetry from Td. The most possible geometry of the core excited CH4** is determined as the C3v symmetry; the core excited CH4** molecules have the same bond angle (109.5? as that of the ground state CH4 and consist of one shorter bond length (1.91 a. u.) and three longer bond lengths (2.04 a. u.). The three longer bond lengths are almost the same as that of the ground state CH4, and the averaged bond length (2.01 a.u.) of core excited CH4** is shorter than that of the ground state CH4(2.06 a.u.).
基金supported by the National Natural Science Foundation of China (Grant Nos.92150105,12227807,and 12241407)the Science and Technology Commission of Shanghai Municipality (Grant Nos.21ZR1420100,and 23JC1402000)support by a grant from the U.S.Department of Energy,Division of Chemical Sciences,Atomic,Molecular and Optical Sciences Program (Grant No.DESC0001771)。
文摘Photoionization can generally be decomposed into a photoabsorption process plus a half-scattering process.The streaking time delay observed in the attosecond streak camera,correspondingly,can be decomposed into a photoabsorption time delay and a continuum time delay.We propose a self-consistent method to account for the potential-laser coupling effect and extract the intrinsic absorption time delay,without invoking an implicit assumption of a constant continuum correction made in previous streaking studies.The concept is based on an iterative technique starting from an initial guess of the absorption time delay and using classical electron trajectories to consistently remove the coupling-induced momentum shift to the streak signal.We show that the self-consistent iterative algorithm converges quickly and is robust against different initial guesses.The method is applied to laser-induced ionization of atoms to obtain the absorption time delay in resonant two-photon ionization and to explore possible time delays in above-threshold ionization.The results confirm an absorption time delay linearly dependent on the ionizing pulse duration in resonant two-photon ionization.The method is also shown to perform better than conventional methods and to identify a small negative absorption time delay(less than 2 attoseconds) in above-threshold ionization.
基金Supported by the Ministry of Science and Technology and the Ministry of Education of China, the Key Project of the Ministry of Education of China （No 306020）, the National Natural Science Foundation of China under Grant No 10574162, the National High-Tech ICF Committee in China, the National Basic Research Programme of China under Grant Nos 2001CB610508 and 2006CB921408, and the Yin-He Super-computer Center, Institute of Applied Physics and Mathematics, Beijing, China,
文摘In the framework of quantum defect theory, we study super-excited states of F2 molecules which can dissociate into F^＋ （^3P2,1,0） and F^-（^1 So） ion-pair. Based on our calculation, we present a vibrational resolved assignment of the high precision photofragment yield spectra for F^- from the F2 ion-pair production.
基金the National Natural Science Foundation of China(NSFC)for financial support under grants No.10074063The Chinese Academy of Science under No.KJ952-S1-418supported by 100-Talent Reasearch Program of The Chinese Academy of Sciences.
文摘Valence band photoemission spectra (PES) for both bulk and nanocrystal CeO2 have been measured on and off resonance of Ce 4d-4f absorption edge. The PES show that the bulk and nanocrystal CeO2 of diameter ranging from 8nm to 50nm exhibit a peak near Fermi edge with binding energy of about 1.8eV. The 1.8eV peak shows a strong dependence on excitation energy, although it looks like the contribution of Ce3+ ion following the data reported in literatures. However, according to the results of resonance photoemission and X-ray absorption spectra at 1s edge, this electronic structure may be associated to the intermediate state charge transfer effects.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674034 and 11564033)the Foundation of President of the China Academy of Engineering Physics(Grant No.2014-1-029)
文摘In the present paper, the time-resolved transient absorption spectroscopy of helium atoms is investigated based on the three-level modeling. The helium atoms are subjected to an extreme ultraviolet （XUV） attosecond pulse and a time-delayed infrared （IR） few-cycle laser field. The odd excited state are populated from the ground state by the XUV pulse due to the dipole selection rule, and probed by the time-delayed IR laser. The time-resolved transient absorption spectroscopy based on the different coupling mechanism demonstrate some different features, the photoabsorption spectrum based on three-level model with rotating wave approximation （RWA） cannot repeat the fast oscillation and the sideband structure which have been observed in the previous experimental investigation. The dressing effect of IR laser pulse on the ground state can contribute new interference structures in the photoabsorption spectrum.
基金realized within the framework of the PNR project 8/423/4388support from the Algerian Ministry of Higher Education and ANDRU。
文摘This work reports pressure-broadening line-wing and line-core of the lithium Li(2p←2s)resonance line perturbed by ground sodium Na(3s)atoms.In far-wing regions,the calculations are performed quantum-mechanically and are intended to examine the photoabsorption coefficients at diverse temperatures.The results show the existence of three satellites,in the blue wing near the wavelengths 470 nm and in the red wing around 862 nm and 1070 nm.For the line-core region,by adopting the simplified Baranger model,the line-width and line-shift rates are determined,and their variation law with temperature is examined.No published data were found to compare these results with.
文摘In nuclear ab initio calculations,nucleon-nucleon interactions are softened via renormalization in order to improve the convergence of calculations.The high-momentum and high-excitation properties of nuclei are not well investigated quantitatively with softened interactions to identify where they may lose predictive power though the low energy observables remain nearly unchanged after the renormalization.In this work,we study nuclear high-mo-mentum properties and high-excitation properties with realistic interactions taking the simplest nucleus,i.e.,deuter-on,as an example.In particular,we study the nucleon momentum distribution and photoabsorption cross section with a chiral effective field theory interaction at N^(3)LO and two softened interactions based on it,i.e.,N^(3)LO-SRG and Daejeon16 interactions.We find that the nucleon momentum distributions of the deuteron calculated with these two soft interactions are significantly suppressed at momenta above 200 MeV in comparison to those calculated with the N^(3)LO chiral interaction.The photoabsorption cross sections of the deuteron calculated with these three interac-tions are overall in agreement with the experimental data.The N^(3)LO-SRG results deviate slightly from the experi-mental data above about 15 MeV due to the renormalization process.The Daejeon16 results deviate more apparently from the experimental data above the peak value compared to the N^(3)LO-SRG results due to the phase equivalent transformations.
