Electric dipole polarizabilities of atoms are very important in many different physical applications, such as the precision atomic frequency standard. Calculations of these properties are very important and challengin...Electric dipole polarizabilities of atoms are very important in many different physical applications, such as the precision atomic frequency standard. Calculations of these properties are very important and challenging. We propose a calculation strategy to calculate the frequency dependent dipole polarizabilities with high precision variationally by using a set of high quality orbital bases where the electron correlations can be taken into account adequately. The static polarizabilitiez of the ground state of Na are calculated accurately by such a method and can be compared with precision experiment measurement directly. The calculation result is in excellent agreement with the available experimental measurements within about 0.1~, which demonstrates the validity of our strategy. Our calculation strategy has a wide usage, not only in polarizibilies, but also in other fields such as theoretical treatment of electron-atom scattering processes. Using the same orbital bases, we carry out precision calculation of Na- affinities. Our calculated affinity is in excellent agreement with precision laser spectroscopy measurements within 0. 1%.展开更多
In order to provide abundant atomic data for fusion research in the stage of precision physics, a scenario, being a combination of indispensable theoretical calculations and bench-mark experimental measurements, is pr...In order to provide abundant atomic data for fusion research in the stage of precision physics, a scenario, being a combination of indispensable theoretical calculations and bench-mark experimental measurements, is proposed. Such abundant atomic data are compiled mainly by theoretical calculations. Accuracies of such abundant data （i.e., atomic energy levels and cor- responding cross sections） are ascertained only by a finite number of bench-mark experimental measurements based on analytical calculation of scattering matrices.展开更多
The binding energy spectrum of all valence orbitals and the momentum distributions of highest occupied molecular orbital （HOMO： 8ag）, 7bu＋7ag, 4bu, 2bg ＋4ag and 2au in 1, 4-dioxane are investigated by electron mo...The binding energy spectrum of all valence orbitals and the momentum distributions of highest occupied molecular orbital （HOMO： 8ag）, 7bu＋7ag, 4bu, 2bg ＋4ag and 2au in 1, 4-dioxane are investigated by electron momentum spectroscopy （EMS） with 600 eV impact energy. The experimental results are consistent with theoretical calcula- tions of C2h chair conformation using the Hartree-Fock method and density functional theory with 6-311＋＋G^＊＊ and AUG-CC-PVTZ basis sets.展开更多
We report the first measurements of the momentum profiles of highest occupied molecular orbital （HOMO） and the complete valence shell binding energy spectra of cyclopentanone with impact energies of 600 and 1200 eV ...We report the first measurements of the momentum profiles of highest occupied molecular orbital （HOMO） and the complete valence shell binding energy spectra of cyclopentanone with impact energies of 600 and 1200 eV by a binary （e, 2e） spectrometer. The experimental momentum profiles of the HOMO orbital are compared with the theoretical momentum distribution calculated using the Hartree Fock and density functional theory methods with various basis sets. However, none of these calculations gives a completely satisfactory description of the momentum distributions of the HOMO 762. The inadequacy of the calculations could result in the intensity difference of the second maximum at p-1.2a.u. between the experiment and the theory. The discrepancy between experimental and theoretical data in the low-momentum region is explained with the distorted wave effect.展开更多
The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy sp...The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy spectra as well as the individual orbital momentum profiles have been measured by using a high resolution （e, 2e） electron momentum spectrometer （EMS） at an impact energy of 1200eV plus the binding energy, and using symmetric noncoplanar kinematics. The experimental orbital electron momentum profiles are compared with self-consistent field （SCF） theoretical profiles calculated using the Hartree-Fock approximation and Density Functional theory predictions in the target Kohn-Sham approximation which includes some treatment of correlation via the exchange and correlation potentials with a range of basis sets. The pole strengths of the main ionization peaks from the inner valence orbitals are estimated.展开更多
Based on the characteristics of valence bonds and the first-principle molecular dynamics simulation we present an optimum valence bond scheme to study properties of important critical clusters with limited computation...Based on the characteristics of valence bonds and the first-principle molecular dynamics simulation we present an optimum valence bond scheme to study properties of important critical clusters with limited computational effort. The differences between the second-row and the third-row elements belonging to the same families can be understood by examining electronic structures and geometric structures even for small size clusters.展开更多
With our newly developed method, we calculate the spin-orbit splitting states 5e1/2 and 5e3/2 of the CF3I molecule incorporating the relativistic effects. Our theoretical results agree excellently with the recent expe...With our newly developed method, we calculate the spin-orbit splitting states 5e1/2 and 5e3/2 of the CF3I molecule incorporating the relativistic effects. Our theoretical results agree excellently with the recent experimental observations. The present study shows that relativistic effects can evidently change the electron momentum distributions of molecular orbitals when a medium Z element is included, such as iodine.展开更多
We have studied the radiation of a double-walled carbon nanotube （DWNT） filament with a length of 4.5 mm and a diameter of 10μm by applying an electric current through the filament. The DWNT filament starts emittin...We have studied the radiation of a double-walled carbon nanotube （DWNT） filament with a length of 4.5 mm and a diameter of 10μm by applying an electric current through the filament. The DWNT filament starts emitting incandescent light at voltage U =6V. Emission spectra of the DWNT below temperature 1250K can well be fitted to those of the blackbody radiation. The intensity of the incandescent light shows an exponential dependence on the voltage applied on the DWNT filaments. The resistance of the DWNT filaments is very stable at high temperatures between 900 and 1250 K during the emission of light in the experiments.展开更多
The accurate atomic data of nitrogen and nitrogen-like ions have an importance role in fusion plasma studies and astrophysics studies. The precise calculation of fine-structures is required to obtain such atomic data....The accurate atomic data of nitrogen and nitrogen-like ions have an importance role in fusion plasma studies and astrophysics studies. The precise calculation of fine-structures is required to obtain such atomic data. Along the whole nitrogen isoelectronic sequence, the contributions of the electron correlations, the Breit interactions and the quantum electrodynamics corrections oi1 the ground-state fine-structures are elucidated. When Z is low, the electron correlations are important, and the Breit interactions, which cannot be neglected cause interesting anomalous fine-structure splittings. When Z is high, the electron correlations are less important, and the Breit interactions are important in addition to spin-orbit interactions for precise calculations.展开更多
We present results of first-principle study for both neutral and anionic onion-like [As@Ni12@As20]. The groundstates of singly-charged and doubly-charged anions deviate from ideal Ih symmetrical geometry because of Ja...We present results of first-principle study for both neutral and anionic onion-like [As@Ni12@As20]. The groundstates of singly-charged and doubly-charged anions deviate from ideal Ih symmetrical geometry because of Jahn-Teller effect, whereas the triply-charged singlet and neutral quartet have similar stable geometries of Ih symmetry. The infrared and Raman spectra may provide a way to determine various charge states of this molecule with the same symmetry. Based on our systematical calculations, we suggest additional experimental measurements in order to determine the appropriate functional with great confidence, which should be important in the research for future quantum dot devices.展开更多
We present our studies of recombination processes of H^2＋, HD^＋ and D^＋2 with high-energy electrons based on a time-dependent wave packet dynamics method. The final vibrational distributions of the products （H2, H...We present our studies of recombination processes of H^2＋, HD^＋ and D^＋2 with high-energy electrons based on a time-dependent wave packet dynamics method. The final vibrational distributions of the products （H2, HD and D2） have been studied. The isotope effects of the final vibrational distributions and their dependence on initial states are elucidated. The study of the final vibrational distributions is relevant to the infrared gas laser researches.展开更多
Using a series of quantum correlated photon pairs, we propose a theoretical scheme for any-to-any multi-user quantum key distribution network based on differential phase shift. The differential phase shift and the dif...Using a series of quantum correlated photon pairs, we propose a theoretical scheme for any-to-any multi-user quantum key distribution network based on differential phase shift. The differential phase shift and the different detection time slots ensure the security of our scheme against eavesdropping. We discuss the security under the intercept-resend attack and the source replacement attack.展开更多
The significant modifications to our recently constructed electron momentum spectrometer have been implemented. Compared with our previous report, the energy and the angle resolutions are significantly improved and re...The significant modifications to our recently constructed electron momentum spectrometer have been implemented. Compared with our previous report, the energy and the angle resolutions are significantly improved and reach △E = 0.45 eV, △θ = ±0.53° and △φ = ±0.84°, respectively. Moreover, the details of data reduction and the relation between azimuthal angle range and the sensitivity are discussed.展开更多
Using the multi-configuration Dirac Fock method including the Breit interactions and QED corrections, we calculate the fine-structure energy levels of the 2^3 Po, 1,2 states along the helium isoelectronic sequence wit...Using the multi-configuration Dirac Fock method including the Breit interactions and QED corrections, we calculate the fine-structure energy levels of the 2^3 Po, 1,2 states along the helium isoelectronic sequence with atomic number up to Z = 36, where LS-coupling is appropriate. Our calculation results agree with the experimental results within about 1%. We elucidate the mechanism of the interesting fine-structure splittings for the 2^3Po,1,2 states along the helium isoelectronic sequence, i.e. the competitions between the spin-orbit interactions and the Breit interactions which represent the relativistic retardation effect of electromagnetic interactions.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
We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant- tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the ...We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant- tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the bias step of the external bias voltage applied on the device has an important effect on the final current-voltage （I - V） curves. The results show that different bias step applied on the device can change the bistability, hysteresis and current plateau structure of the I - V curve. The current plateau occurs only in the case of small bias step. As the bias step increases, this plateau structure disappears.展开更多
In the frame work of quantum defect theory, photoabsorption spectra near Si 219 edges of silane have been studied. When silanes are adsorbed on a physical surface and excited by polarized x-ray photons, relative inten...In the frame work of quantum defect theory, photoabsorption spectra near Si 219 edges of silane have been studied. When silanes are adsorbed on a physical surface and excited by polarized x-ray photons, relative intensities of the spectra will be different from that of free molecules. Such features can be used to determine orientations of adsorbed silanes based on selection rules.展开更多
In the framework of quantum defect theory, we calculate photoabsorption cross sections of Na^＋ 2. Based on our calculations, there is an absorption window in the photoabsorption cross sections of Na^＋ 2. and more th...In the framework of quantum defect theory, we calculate photoabsorption cross sections of Na^＋ 2. Based on our calculations, there is an absorption window in the photoabsorption cross sections of Na^＋ 2. and more than one bump above the absorption window. The calculated photoabsorption cross sections provide an explanation for the abnormal bump in the experimental measurements of Hudson, which is a long-standing experimental puzzle.展开更多
Using a modified R-matrix code, the fine-structure-resolved partial photoionization cross sections of excited Na （Z = 11） are calculated within the Breit-Pauli approximation. Our calculated energy levels of Na＋ and...Using a modified R-matrix code, the fine-structure-resolved partial photoionization cross sections of excited Na （Z = 11） are calculated within the Breit-Pauli approximation. Our calculated energy levels of Na＋ and Na are in good agreement with the experimental values within 1% and the branching ratios of the J-resolved partial cross sections are consistent with the recent measurements within the experimental uncertainties. The agreements are impossible to be obtained without adequately taking into account the relativistic effects and the electron correlations together. Therefore, even for the intermediate-Z elements （e.g. Na with Z = 11）, the relativistic effects （mainly the spin-orbit interactions） should not be neglected.展开更多
Single wall carbon nanotubes with small diameters （〈 5.0 A） subjected to bending deformation are simulated by orthogonal tight-binding molecular dynamics approach. Based on the calculations of C-C bond stretching a...Single wall carbon nanotubes with small diameters （〈 5.0 A） subjected to bending deformation are simulated by orthogonal tight-binding molecular dynamics approach. Based on the calculations of C-C bond stretching and breaking in the bending nanotubes, we elucidate the atomistic failure mechanisms of nanotube with small diameters. In the folding zone of bending nanotube, a large elongation of C-C bonds occurs, accounting for the superelastic behaviour. The C-C bonds parallel to the axis direction of nanotube are broken firstly due to the sustained longitudinal stretching strain, giving rising to forming one-notch or two-notch bond-breaking mode depending on nanotube chirMities. The direct bond-breaking mechanism is responsible for the brittle fracture behaviour of nanotubes with small diameters.展开更多
基金Supported by the Ministry of Science and Technology and Ministry of Education of China, the Key grant Project of the Ministry of Education of China （No 306020）, the National Natural Science Foundation of China under Grant Nos 10734040 and 10905040, the National High-Tech ICF Committee in China, the Yin-He Super-computer Center, Institute of Applied Physics and Mathematics, Beijing, China, and the National Basic Research Program of China under Grant No 2006CB921408.
文摘Electric dipole polarizabilities of atoms are very important in many different physical applications, such as the precision atomic frequency standard. Calculations of these properties are very important and challenging. We propose a calculation strategy to calculate the frequency dependent dipole polarizabilities with high precision variationally by using a set of high quality orbital bases where the electron correlations can be taken into account adequately. The static polarizabilitiez of the ground state of Na are calculated accurately by such a method and can be compared with precision experiment measurement directly. The calculation result is in excellent agreement with the available experimental measurements within about 0.1~, which demonstrates the validity of our strategy. Our calculation strategy has a wide usage, not only in polarizibilies, but also in other fields such as theoretical treatment of electron-atom scattering processes. Using the same orbital bases, we carry out precision calculation of Na- affinities. Our calculated affinity is in excellent agreement with precision laser spectroscopy measurements within 0. 1%.
基金supported by Ministry of Science and Technology and Ministry of Education of Chinathe Key grant Project of Chinese Ministry of Education (No.306020)+2 种基金National Natural Science Foundation of China (Nos. 10734040, 10905040)the National High-Tech ICF Committee in China and the Yin-He Super-computer Center, Institute of Applied Physics and Mathematics, Beijing, ChinaNational Basic Research Program of China (No.2006CB921468)
文摘In order to provide abundant atomic data for fusion research in the stage of precision physics, a scenario, being a combination of indispensable theoretical calculations and bench-mark experimental measurements, is proposed. Such abundant atomic data are compiled mainly by theoretical calculations. Accuracies of such abundant data （i.e., atomic energy levels and cor- responding cross sections） are ascertained only by a finite number of bench-mark experimental measurements based on analytical calculation of scattering matrices.
基金Supported bv the National Natural Science Foundation of China under Grant No 10575062, and the Specialized Research Fund for the Doctoral Programme of Higher Education under Grant No 20050003084.
文摘The binding energy spectrum of all valence orbitals and the momentum distributions of highest occupied molecular orbital （HOMO： 8ag）, 7bu＋7ag, 4bu, 2bg ＋4ag and 2au in 1, 4-dioxane are investigated by electron momentum spectroscopy （EMS） with 600 eV impact energy. The experimental results are consistent with theoretical calcula- tions of C2h chair conformation using the Hartree-Fock method and density functional theory with 6-311＋＋G^＊＊ and AUG-CC-PVTZ basis sets.
基金Supported by the National Natural Science Foundation of China under Grant No 10575062, and the Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20050003084.
文摘We report the first measurements of the momentum profiles of highest occupied molecular orbital （HOMO） and the complete valence shell binding energy spectra of cyclopentanone with impact energies of 600 and 1200 eV by a binary （e, 2e） spectrometer. The experimental momentum profiles of the HOMO orbital are compared with the theoretical momentum distribution calculated using the Hartree Fock and density functional theory methods with various basis sets. However, none of these calculations gives a completely satisfactory description of the momentum distributions of the HOMO 762. The inadequacy of the calculations could result in the intensity difference of the second maximum at p-1.2a.u. between the experiment and the theory. The discrepancy between experimental and theoretical data in the low-momentum region is explained with the distorted wave effect.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 19854002, 19774037 and 10274040） and the Research Fund for the Doctoral Program Foundation of Institution of Higher Education of China （Grant No 1999000327）.
文摘The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy spectra as well as the individual orbital momentum profiles have been measured by using a high resolution （e, 2e） electron momentum spectrometer （EMS） at an impact energy of 1200eV plus the binding energy, and using symmetric noncoplanar kinematics. The experimental orbital electron momentum profiles are compared with self-consistent field （SCF） theoretical profiles calculated using the Hartree-Fock approximation and Density Functional theory predictions in the target Kohn-Sham approximation which includes some treatment of correlation via the exchange and correlation potentials with a range of basis sets. The pole strengths of the main ionization peaks from the inner valence orbitals are estimated.
基金Supported by the Ministry of Science and Technology and Ministry of Education of China, the Key Project of the Ministry of Education of China under Grant No 306020, the National Natural Science Foundation of China under Grant No 10314010, the National High-Tech ICF Committee in China and the Yin-He Super-computer Center, Institute of Applied Physics and Mathematics, Beijing, China, and the State Key Basic Research and Development Programme of China under Grant No 2001CB610508.
文摘Based on the characteristics of valence bonds and the first-principle molecular dynamics simulation we present an optimum valence bond scheme to study properties of important critical clusters with limited computational effort. The differences between the second-row and the third-row elements belonging to the same families can be understood by examining electronic structures and geometric structures even for small size clusters.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10874097, 10704046 and 10575062, and the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20070003146.
文摘With our newly developed method, we calculate the spin-orbit splitting states 5e1/2 and 5e3/2 of the CF3I molecule incorporating the relativistic effects. Our theoretical results agree excellently with the recent experimental observations. The present study shows that relativistic effects can evidently change the electron momentum distributions of molecular orbitals when a medium Z element is included, such as iodine.
文摘We have studied the radiation of a double-walled carbon nanotube （DWNT） filament with a length of 4.5 mm and a diameter of 10μm by applying an electric current through the filament. The DWNT filament starts emitting incandescent light at voltage U =6V. Emission spectra of the DWNT below temperature 1250K can well be fitted to those of the blackbody radiation. The intensity of the incandescent light shows an exponential dependence on the voltage applied on the DWNT filaments. The resistance of the DWNT filaments is very stable at high temperatures between 900 and 1250 K during the emission of light in the experiments.
基金Supported by the Ministry of Science and Technology and the Ministry of Education of China, the Key Project of Ministry of Education of China under Grant NO 306020, the National Natural Science Foundation of China under Grant No 10734040, the National High-Tech ICF Committee in China, the Yin-He Super-computer Center, Institute of Applied Physics and Mathematics, Beijing, China, and the National Basic Research Program of China under Grant No 2006CB921408.
文摘The accurate atomic data of nitrogen and nitrogen-like ions have an importance role in fusion plasma studies and astrophysics studies. The precise calculation of fine-structures is required to obtain such atomic data. Along the whole nitrogen isoelectronic sequence, the contributions of the electron correlations, the Breit interactions and the quantum electrodynamics corrections oi1 the ground-state fine-structures are elucidated. When Z is low, the electron correlations are important, and the Breit interactions, which cannot be neglected cause interesting anomalous fine-structure splittings. When Z is high, the electron correlations are less important, and the Breit interactions are important in addition to spin-orbit interactions for precise calculations.
基金Project supported by the Ministry of Science and Technology （Grant No 2001CB610508）, the Ministry of Education of China, and the National Natural Science Foundation of China （Grant No 10314010）.
文摘We present results of first-principle study for both neutral and anionic onion-like [As@Ni12@As20]. The groundstates of singly-charged and doubly-charged anions deviate from ideal Ih symmetrical geometry because of Jahn-Teller effect, whereas the triply-charged singlet and neutral quartet have similar stable geometries of Ih symmetry. The infrared and Raman spectra may provide a way to determine various charge states of this molecule with the same symmetry. Based on our systematical calculations, we suggest additional experimental measurements in order to determine the appropriate functional with great confidence, which should be important in the research for future quantum dot devices.
基金Supported by the National Key Basic Research and Development Programme of China under Grant No 2001CB610508, the Ministry of Education of China, the National Natural Science foundation of China under Grant No 10314010, the National HighTech ICF Committee in China, and the Yin-He Super-Computer Center, Institute of Applied Physics and Mathematics, Beijing, China.
文摘We present our studies of recombination processes of H^2＋, HD^＋ and D^＋2 with high-energy electrons based on a time-dependent wave packet dynamics method. The final vibrational distributions of the products （H2, HD and D2） have been studied. The isotope effects of the final vibrational distributions and their dependence on initial states are elucidated. The study of the final vibrational distributions is relevant to the infrared gas laser researches.
基金Supported by the National Key Basic Research Programme of China under Grant No 2006CB921106, the National Natural Science Foundation of China under Grant Nos 10325521 and 60433050, and the SRFDP Programme of the Ministry of Education of China, and the Key Project of the Ministry of Education of China under Grant No 306020.
文摘Using a series of quantum correlated photon pairs, we propose a theoretical scheme for any-to-any multi-user quantum key distribution network based on differential phase shift. The differential phase shift and the different detection time slots ensure the security of our scheme against eavesdropping. We discuss the security under the intercept-resend attack and the source replacement attack.
基金supported by the National Natural Science Foundation of China (Grant No 10575062)Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No 20050003084)
文摘The significant modifications to our recently constructed electron momentum spectrometer have been implemented. Compared with our previous report, the energy and the angle resolutions are significantly improved and reach △E = 0.45 eV, △θ = ±0.53° and △φ = ±0.84°, respectively. Moreover, the details of data reduction and the relation between azimuthal angle range and the sensitivity are discussed.
基金Supported by the Ministry of Science and Technology and 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 10734040, the National High-Tech ICF Committee in China, and the Yin-He Super-Computer Center, Institute of Applied Physics and Mathematics, Beijing, China, and the National Basic Research Programme of China under Grant No 2006CB921408.
文摘Using the multi-configuration Dirac Fock method including the Breit interactions and QED corrections, we calculate the fine-structure energy levels of the 2^3 Po, 1,2 states along the helium isoelectronic sequence with atomic number up to Z = 36, where LS-coupling is appropriate. Our calculation results agree with the experimental results within about 1%. We elucidate the mechanism of the interesting fine-structure splittings for the 2^3Po,1,2 states along the helium isoelectronic sequence, i.e. the competitions between the spin-orbit interactions and the Breit interactions which represent the relativistic retardation effect of electromagnetic interactions.
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Supported by the National Natural Science Foundation of China under Grant No 10404022, and the National Basic Research Programme of China under Grant No G2000067107.
文摘We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant- tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the bias step of the external bias voltage applied on the device has an important effect on the final current-voltage （I - V） curves. The results show that different bias step applied on the device can change the bistability, hysteresis and current plateau structure of the I - V curve. The current plateau occurs only in the case of small bias step. As the bias step increases, this plateau structure disappears.
基金Supported by the Ministry of Science and Technology and 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 2006CB921400, and the Yin-He Super-Computer Center, Institute of Applied Physics and Mathematics, Beijing, China.
文摘In the frame work of quantum defect theory, photoabsorption spectra near Si 219 edges of silane have been studied. When silanes are adsorbed on a physical surface and excited by polarized x-ray photons, relative intensities of the spectra will be different from that of free molecules. Such features can be used to determine orientations of adsorbed silanes based on selection rules.
基金Supported by the Ministry of Science and Technology and Ministry of Education of China, the Key Project of the Ministry of Education of China （No 306020）, the National Natural Science Foundation of China, the National High-Tech ICF Committee in China and the Yin-He Super-coInputer Center, Institute of Applied Physics and Mathematics, Beijing, China, the National Basic Research Programme of China under Grant No 2006CB921400 and the National Natural Science Foundation of China under Grant No 10574162.
文摘In the framework of quantum defect theory, we calculate photoabsorption cross sections of Na^＋ 2. Based on our calculations, there is an absorption window in the photoabsorption cross sections of Na^＋ 2. and more than one bump above the absorption window. The calculated photoabsorption cross sections provide an explanation for the abnormal bump in the experimental measurements of Hudson, which is a long-standing experimental puzzle.
基金Supported by This work is supported by the Ministry of Science and Technology and Ministry of Education of China, the Key Project of the Ministry of Education of China （N0 306020）, the National Natural Science Foundation of China, the National High- Tech ICF Committee in China and the Yin-He Super-computer Center, Institute of Applied Physics and Mathematics, Beijing, China, and the National Basic Research Programme of China under Grant No 2006CB921408.
文摘Using a modified R-matrix code, the fine-structure-resolved partial photoionization cross sections of excited Na （Z = 11） are calculated within the Breit-Pauli approximation. Our calculated energy levels of Na＋ and Na are in good agreement with the experimental values within 1% and the branching ratios of the J-resolved partial cross sections are consistent with the recent measurements within the experimental uncertainties. The agreements are impossible to be obtained without adequately taking into account the relativistic effects and the electron correlations together. Therefore, even for the intermediate-Z elements （e.g. Na with Z = 11）, the relativistic effects （mainly the spin-orbit interactions） should not be neglected.
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 under Grant No 306020, the National Natural Science Foundation of China under Grant Nos 10314010 and 50525208, the National High-Tech ICF Committee in China, the Yin-He Super-computer Center, Institute of Applied Physics and Mathematics, Beijing, China, and the State Key Basic Research and Development Programme of China under Grant No 2001CB610508.
文摘Single wall carbon nanotubes with small diameters （〈 5.0 A） subjected to bending deformation are simulated by orthogonal tight-binding molecular dynamics approach. Based on the calculations of C-C bond stretching and breaking in the bending nanotubes, we elucidate the atomistic failure mechanisms of nanotube with small diameters. In the folding zone of bending nanotube, a large elongation of C-C bonds occurs, accounting for the superelastic behaviour. The C-C bonds parallel to the axis direction of nanotube are broken firstly due to the sustained longitudinal stretching strain, giving rising to forming one-notch or two-notch bond-breaking mode depending on nanotube chirMities. The direct bond-breaking mechanism is responsible for the brittle fracture behaviour of nanotubes with small diameters.
