To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross s...To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section(FAST) spectrometer has been designed based on a Cs2Li La Br6(CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and γ-rays was evaluated with different 6Li/7 Li abundance ratios using Geant4. The neutron-γdiscrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs,and light readout modes. A cubic 6Li-enriched( > 90%) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the Φ 50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-γ discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.展开更多
The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energ...The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energy was determined by the neutron total cross-section spectrometer using the time-of-flight technique.A fast multi-cell fission chamber was used as the neutron detector,and a 10-mm-thick high-purity natural lead sample was employed for the neutron transmission measurements.The on-beam background was determined using Co,In,Ag,and Cd filters.The excitation function of ^(nat)Pb(n,tot)reaction below 20 MeV was calculated using the TALYS-1.96 nuclear-reaction modeling program.The present results were compared with previous results,the evaluated data available in the five major evaluated nuclear data libraries(i.e.,ENDF/B-VIII.0,JEFF-3.3,JENDL-5,CENDL-3.2,and BROND-3.1),and the theoretical calculation curve.Good agreement was found between the new results and those of previous experiments and with the theoretical curves in the corresponding region.This measurement obtained the neutron total cross section of natural lead with good accuracy over a wide energy range and added experimental data in the resonance energy range.This provides more reliable experimental data for nuclear engineering design and nuclear data evaluation of lead.展开更多
A complex optical model potential modified by incorporating the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is first employed to ca...A complex optical model potential modified by incorporating the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is first employed to calculate the total cross sections for electrons scattering from such complex molecules as C2H6, C2F6, C6H6 and C6F6 using the aclditivity rule model at Hartree-Fock level over the energy range from 100 eV to 5000 eV. The total cross sections are quantitatively compared with those obtained by experiments wherever available, and they are in good agreement with each other over a wide energy range. It is shown that the modified potential together with the additivity rule model is completely suitable for the calculation of total cross sections of electrons scattering from such complex molecules as C2H6, C2F6, C6H6 and C6F6 above 200 eV-300 eV.展开更多
A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds, is employed to calculate the total cross sections for electrons scatt...A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds, is employed to calculate the total cross sections for electrons scattering from simple molecules （SO2, H2S, OCS, CS2 and SO3） containing the larger atom, sulfur, at 30-5000eV by using the additivity rule model at Hartree-Fock level. The quantitative molecular total cross section results are compared with those obtained in experiments and other calculations wherever available, and good agreement is obtained. It is shown that the additivity rule model together with the complex optical model potential modified by the concept of bonded atom can give the results closer to the experiments than the one unmodified by it. So, the introduction of bonded-atom concept in complex optical model potential betters the accuracy of the total cross section calculations of electrons from the molecules containing the larger atom, sulfur.展开更多
Taking into consideration the changes of the geometric shielding effect in a molecule as the energy of incident electrons varies, this paper presents an empirical fraction, which depends on the energy of incident elec...Taking into consideration the changes of the geometric shielding effect in a molecule as the energy of incident electrons varies, this paper presents an empirical fraction, which depends on the energy of incident electrons, the target＇s molecular dimension and the atomic and electronic numbers in the molecule. Using this empirical fraction, it proposes a new formulation of the additivity rule. Employing the new additivity rule, it calculates the total cross sections of electron scattering by C2H4, C6H6, C6H14 and C8H18 over the energy range from 50 to 5000eV. In order to exclude the calculation deviations caused by solving the radial Schrodinger equation of electron scattering by atoms, here the atomic cross sections are derived from the experimental total cross section results of simple molecules （H2, O2, CO） via the inversion algorithm. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, even at energy of several tens of eV.展开更多
The original additivity rule method cannot give good results for electron scattering from SO,SO2,SO2Cl2,SO2ClF,and SO2F2 molecules at low energy,because the electron-molecule scattering is simply reduced to electron-a...The original additivity rule method cannot give good results for electron scattering from SO,SO2,SO2Cl2,SO2ClF,and SO2F2 molecules at low energy,because the electron-molecule scattering is simply reduced to electron-atom scattering.Considering the difference between the bound atom in a molecule and the corresponding free atom,the original additivity rule is revised.With the revised additivity rule,the total cross sections for electron scattering from these molecules are calculated over a wide energy range below 3000 eV and compared with the available experimental and theoretical data.A better agreement between them is obtained.展开更多
The additivity rule for electron-molecule scattering is revised by considering the difference between the free atom and the bound atom in the molecule. The total cross sections for electron scattering from fluorometha...The additivity rule for electron-molecule scattering is revised by considering the difference between the free atom and the bound atom in the molecule. The total cross sections for electron scattering from fluoromethanes （CF4, CF3H, CF2H2, and CFH3） are calculated in an energy range from 100 eV to 1500 eV by the revised additivity rule. The present calculations are compared with the original additivity rule results and the available experimental data. Better agreement with each other is obtained.展开更多
A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cr...A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross sections （TCS5） for electrons scattering from several molecules （CF4, CCl4, CFCl3, CF2 Cl2, and CF3 Cl） over an incident energy range 30 - 5000 eV using the additivity rule model at Hartre-Fock level. The quantitative TCS5 are compared with those obtained by experiments and other theories wherever available, and good agreement is obtained above 100 eV. It is shown that the modified potential can successfully calculate the TCS5 of electron-molecule scattering over a wide energy range, especially at lower energies.展开更多
A complex optical model potential correlated by the concept of bonded atom, which considers the overlapping effect of electron clouds between two atoms in a molecule, is firstly employed to calculate the total cross s...A complex optical model potential correlated by the concept of bonded atom, which considers the overlapping effect of electron clouds between two atoms in a molecule, is firstly employed to calculate the total cross sections for electron scattering on several molecules (NH3, H2O, CH4, CO, N2, O2, and C2H4) over the energy range 10 ～ 5000 eV using the additivity rule model at Hartree-Fock level. The difference between the bonded atom and the free one in states is that the overlapping effect of electron clouds of bonded atoms in a molecule is considered. The quantitative total cross sections are compared with the experimental data and with the other calculations wherever available and good agreement is obtained over the energy range 10 ～ 5000 eV. It is shown that the correlated calculations are much closer to the available experimental data than the uncorrelated ones at lower energies, especially below 500 eV. Therefore,considering the overlapping effect of electron clouds in the complex optical model potential could be helpful for the better accuracy of the total cross section calculations of electron scattering from molecules.展开更多
A new modified formulation of the Additivity Rule (AR) was proposed to calculate the total electron scattering cross sections for CH4, CO2, NO2, and N2O, considering the overlapping between atoms in molecules and the ...A new modified formulation of the Additivity Rule (AR) was proposed to calculate the total electron scattering cross sections for CH4, CO2, NO2, and N2O, considering the overlapping between atoms in molecules and the not fully transparency of the molecules. The present calculation covers the range of impact energy from 10 to 3000 eV. The results are compared with experimental data and other theories where available. The atoms are presented by spherical complex optical potential, which is composed of static, exchange, polarization, and absorption terms.展开更多
To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The m...To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The measurement is performed at the Back-n white neutron source with a 76-m time-of-flight path using the China Spallation Neutron Source. A multilayer fast fission chamber with 235U and 238U is employed as the neutron detector. The diameter and thickness of the natural graphite sample are 70 mm and 40 mm, respectively. Signal waveforms are collected using a data acquisition system. Off-line data processing was used to obtain the neutron time-of-flight spectra and transmissions. The uncertainty of the counting statistics is generally approximately 3% for each bin in the energy range of 1–20 MeV. It is determined that the results for the neutron total cross section of carbon obtained using ^235U cells are in good agreement with the results obtained using 238U cells within limits of statistical uncertainty. Moreover, the measured total cross sections show good agreement with the broadening evaluated data.展开更多
The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power installations.The neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy...The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power installations.The neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer(NTOX)based on the multi-cell fast fission chamber at the China Spallation Neutron Source(CSNS)-Back-n white neutron source(Back-n).The fission count-neutron energy distributions of ^(235)U and ^(238)U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW.The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV.The neutron total cross section of^(9)Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region.In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV,the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5%and 15%,respectively.In the resonance energy region,the measured resonance energies in our experiment were 0.63,0.82,and 2.8 MeV,respectively.The results showed that the total cross section uncertainties of three Be samples were within 2.2%in the energy region below 1 MeV.The total cross section uncertainty of 30 mm Be from ^(235)U was the smallest and less than 5%in the energy region of 0.3 eV−120 MeV.The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.展开更多
Total cross sections （TCSs） of electrons scattering from triatomic molecules over the energy range from 30 to 5000 eV are investigated employing a new semi-empirical formula. The TCSs of electrons scattering from tr...Total cross sections （TCSs） of electrons scattering from triatomic molecules over the energy range from 30 to 5000 eV are investigated employing a new semi-empirical formula. The TCSs of electrons scattering from triatomic molecules SO2, NO2, and CO2 are calculated. The quantitative TCSs are in good agreement with those obtained by experiments. It is shown that the results derived from the semi-empirical formula are much closer to the measurements than other calculations.展开更多
The total （elastic plus inelastic） cross sections for positron scattering from N2 and CO2 over the incident energy range from 30 to 3000eV are calculated using the additivity rule model at Hartree-Fock level. A comp...The total （elastic plus inelastic） cross sections for positron scattering from N2 and CO2 over the incident energy range from 30 to 3000eV are calculated using the additivity rule model at Hartree-Fock level. A complex optical model potential modified by incorporating the concept of bonded atom, which takes into account the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross section of positron-molecule scattering. The calculated total cross sections are in good agreement with those reported by experiments and other theories over a wide energy range.展开更多
The electron-impact ionization of lithium-like ions C^(3+),N^(4+),O^(5+),Ne^(7+),and Fe2^(3+)is studied using a combination of two-potential distorted-wave and R-matrix methods with a relativistic correction.Total cro...The electron-impact ionization of lithium-like ions C^(3+),N^(4+),O^(5+),Ne^(7+),and Fe2^(3+)is studied using a combination of two-potential distorted-wave and R-matrix methods with a relativistic correction.Total cross sections are computed for incident energies from 1 to 10 times of ionization energy and better agreements with the experimental results are obtained in comparison with the theoretical data available.It is found that the indirect ionization processes become significant for the incident energy larger than about four times of the ionization energy.Contributions from the exchange effects along the isoelectronic sequence are also discussed and found to be important.The present method can be used to obtain systematic ionization cross sections for highly charged ions across a wide incident energy range.展开更多
By using the nuclear reaction model for light nuclei, the calculations of the double-differential cross sections of outgoing neutrons from n ＋^9Be reactions are performed. The total outgoing neutrons are only come fr...By using the nuclear reaction model for light nuclei, the calculations of the double-differential cross sections of outgoing neutrons from n ＋^9Be reactions are performed. The total outgoing neutrons are only come from the （n, 2n）2a reaction channel. The （n, 2n）2a reaction channel is achieved through six different reaction approach, which are illustrated in this paper. The calculated results agree very well with the measured data at En = 7.1, 8.09, 8.17, 9.09, 9.97 and 10.26 MeV, because the updated level schemes related to the n ＋ ^9Be reactions have been employed in this calculations.展开更多
In this work, the elastic cross section is calculated at energies above the Coulomb barrier for 3He + 58Ni using a Woods-Saxon potential. The solutions of the radial Schrödinger equations are calculated numer...In this work, the elastic cross section is calculated at energies above the Coulomb barrier for 3He + 58Ni using a Woods-Saxon potential. The solutions of the radial Schrödinger equations are calculated numerically and they are introduced in the S matrix, after which the cross section is obtained. The parameters in the potential are adjusted to satisfy known experimental data.展开更多
We demonstrate a new technique for calculating proton-proton inelastic cross-section, which allows one by application of the Laplace' method replace the integrand in the integral for the scattering amplitude in th...We demonstrate a new technique for calculating proton-proton inelastic cross-section, which allows one by application of the Laplace' method replace the integrand in the integral for the scattering amplitude in the vicinity of the maximum point by expression of Gaussian type. This, in turn, allows us to overcome the computational difficulties for the calculation of the integrals expressing the cross section to sufficiently large numbers of particles. We have managed to overcome these problems in calculating the proton-proton inelastic cross-section for production (n ≤ 8) number of secondary particles in within the framework of φ3 model. As the result the obtained dependence of inelastic cross-section and total scattering cross-section on the energy √s are qualitative agrees with the experimental data. Such description of total cross-section behavior differs considerably from existing now description, where reggeons exchange with the intercept greater than unity is considered.展开更多
We demonstrate a possibility of computation of inelastic scattering cross-section in a multi-peripheral model by application of the Laplace method to multidimensional integral over the domain of physical process. Foun...We demonstrate a possibility of computation of inelastic scattering cross-section in a multi-peripheral model by application of the Laplace method to multidimensional integral over the domain of physical process. Founded the constrained maximum point of scattering cross-section integral under condition of the energy-momentum conservation. The integrand is substituted for an expression of Gaussian type in the neighborhood of this point. It made possible to compute this integral numerically. The paper has two parts. The hunting procedure of the constrained maximum point is considered and the properties of this maximum point are discussed in the given part of the paper. It is shown that virtuality of all internal lines of the “comb” diagram reduced at the constrained maximum point with energy growth. In the second part of the paper we give some the arguments in favor of consideration of the mechanism of virtuality reduction as the mechanism of the total hadron scattering cross-section growth, which is not taken into account within the framework of Regge theory.展开更多
基金supported by the Key Laboratory of Nuclear Data Foundation(No.JCKY2022201C153)National Natural Science Foundation of China(No.11505216),Educational Commission of Hunan Province of China(No.19B488)Natural Science Foundation of Hunan Province of China(Nos.2021JJ40444 and 2020RC3054).
文摘To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section(FAST) spectrometer has been designed based on a Cs2Li La Br6(CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and γ-rays was evaluated with different 6Li/7 Li abundance ratios using Geant4. The neutron-γdiscrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs,and light readout modes. A cubic 6Li-enriched( > 90%) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the Φ 50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-γ discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.
基金This work is supported by the National Natural Science Foundation of China(No.12375296)the Key Laboratory of Nuclear Data Foundation(No.JCKY2022201C153)+2 种基金the Natural Science Foundation of Hunan Province of China(Nos.2021JJ40444,2020RC3054)the Youth Innovation Promotion Association CAS(No.2023014)the National Key Research and Development Plan(No.2022YFA1603303).
文摘The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energy was determined by the neutron total cross-section spectrometer using the time-of-flight technique.A fast multi-cell fission chamber was used as the neutron detector,and a 10-mm-thick high-purity natural lead sample was employed for the neutron transmission measurements.The on-beam background was determined using Co,In,Ag,and Cd filters.The excitation function of ^(nat)Pb(n,tot)reaction below 20 MeV was calculated using the TALYS-1.96 nuclear-reaction modeling program.The present results were compared with previous results,the evaluated data available in the five major evaluated nuclear data libraries(i.e.,ENDF/B-VIII.0,JEFF-3.3,JENDL-5,CENDL-3.2,and BROND-3.1),and the theoretical calculation curve.Good agreement was found between the new results and those of previous experiments and with the theoretical curves in the corresponding region.This measurement obtained the neutron total cross section of natural lead with good accuracy over a wide energy range and added experimental data in the resonance energy range.This provides more reliable experimental data for nuclear engineering design and nuclear data evaluation of lead.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574039）.
文摘A complex optical model potential modified by incorporating the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is first employed to calculate the total cross sections for electrons scattering from such complex molecules as C2H6, C2F6, C6H6 and C6F6 using the aclditivity rule model at Hartree-Fock level over the energy range from 100 eV to 5000 eV. The total cross sections are quantitatively compared with those obtained by experiments wherever available, and they are in good agreement with each other over a wide energy range. It is shown that the modified potential together with the additivity rule model is completely suitable for the calculation of total cross sections of electrons scattering from such complex molecules as C2H6, C2F6, C6H6 and C6F6 above 200 eV-300 eV.
基金Project supported by the National Natural Science Foundation of China （Grant No 10174019）.
文摘A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds, is employed to calculate the total cross sections for electrons scattering from simple molecules （SO2, H2S, OCS, CS2 and SO3） containing the larger atom, sulfur, at 30-5000eV by using the additivity rule model at Hartree-Fock level. The quantitative molecular total cross section results are compared with those obtained in experiments and other calculations wherever available, and good agreement is obtained. It is shown that the additivity rule model together with the complex optical model potential modified by the concept of bonded atom can give the results closer to the experiments than the one unmodified by it. So, the introduction of bonded-atom concept in complex optical model potential betters the accuracy of the total cross section calculations of electrons from the molecules containing the larger atom, sulfur.
基金Project supported by the National Natural Science Foundation of China (Grant No 10574039)the Program for Science and Technology Innovation Talents in Universities of Henan Province in China (Grant No 2008HASTIT008)
文摘Taking into consideration the changes of the geometric shielding effect in a molecule as the energy of incident electrons varies, this paper presents an empirical fraction, which depends on the energy of incident electrons, the target＇s molecular dimension and the atomic and electronic numbers in the molecule. Using this empirical fraction, it proposes a new formulation of the additivity rule. Employing the new additivity rule, it calculates the total cross sections of electron scattering by C2H4, C6H6, C6H14 and C8H18 over the energy range from 50 to 5000eV. In order to exclude the calculation deviations caused by solving the radial Schrodinger equation of electron scattering by atoms, here the atomic cross sections are derived from the experimental total cross section results of simple molecules （H2, O2, CO） via the inversion algorithm. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, even at energy of several tens of eV.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11204121)the Natural Science Foundation of Shandong Province,China(Grant No. ZR2011AL021)+1 种基金the National Natural Science Foundation of China (Grant No. 11074104)the Discipline Construction Fund of Ludong University,China
文摘The original additivity rule method cannot give good results for electron scattering from SO,SO2,SO2Cl2,SO2ClF,and SO2F2 molecules at low energy,because the electron-molecule scattering is simply reduced to electron-atom scattering.Considering the difference between the bound atom in a molecule and the corresponding free atom,the original additivity rule is revised.With the revised additivity rule,the total cross sections for electron scattering from these molecules are calculated over a wide energy range below 3000 eV and compared with the available experimental and theoretical data.A better agreement between them is obtained.
基金Project supported by the Natural Science Foundation of Shandong Province,China (Grant No. ZR2011AL021)the National Natural Science Foundation of China (Grant No. 11074104)+1 种基金the Research Foundation of Ludong University,China (Grant No. LY20072801)the Discipline Construction Fund of Ludong University,China
文摘The additivity rule for electron-molecule scattering is revised by considering the difference between the free atom and the bound atom in the molecule. The total cross sections for electron scattering from fluoromethanes （CF4, CF3H, CF2H2, and CFH3） are calculated in an energy range from 100 eV to 1500 eV by the revised additivity rule. The present calculations are compared with the original additivity rule results and the available experimental data. Better agreement with each other is obtained.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10174019 and 10574039
文摘A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross sections （TCS5） for electrons scattering from several molecules （CF4, CCl4, CFCl3, CF2 Cl2, and CF3 Cl） over an incident energy range 30 - 5000 eV using the additivity rule model at Hartre-Fock level. The quantitative TCS5 are compared with those obtained by experiments and other theories wherever available, and good agreement is obtained above 100 eV. It is shown that the modified potential can successfully calculate the TCS5 of electron-molecule scattering over a wide energy range, especially at lower energies.
文摘A complex optical model potential correlated by the concept of bonded atom, which considers the overlapping effect of electron clouds between two atoms in a molecule, is firstly employed to calculate the total cross sections for electron scattering on several molecules (NH3, H2O, CH4, CO, N2, O2, and C2H4) over the energy range 10 ～ 5000 eV using the additivity rule model at Hartree-Fock level. The difference between the bonded atom and the free one in states is that the overlapping effect of electron clouds of bonded atoms in a molecule is considered. The quantitative total cross sections are compared with the experimental data and with the other calculations wherever available and good agreement is obtained over the energy range 10 ～ 5000 eV. It is shown that the correlated calculations are much closer to the available experimental data than the uncorrelated ones at lower energies, especially below 500 eV. Therefore,considering the overlapping effect of electron clouds in the complex optical model potential could be helpful for the better accuracy of the total cross section calculations of electron scattering from molecules.
文摘A new modified formulation of the Additivity Rule (AR) was proposed to calculate the total electron scattering cross sections for CH4, CO2, NO2, and N2O, considering the overlapping between atoms in molecules and the not fully transparency of the molecules. The present calculation covers the range of impact energy from 10 to 3000 eV. The results are compared with experimental data and other theories where available. The atoms are presented by spherical complex optical potential, which is composed of static, exchange, polarization, and absorption terms.
基金supported by the National Key Research and Development Plan(No.2016YFA0401603)the National Natural Science Foundation of China(No.11675155)
文摘To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The measurement is performed at the Back-n white neutron source with a 76-m time-of-flight path using the China Spallation Neutron Source. A multilayer fast fission chamber with 235U and 238U is employed as the neutron detector. The diameter and thickness of the natural graphite sample are 70 mm and 40 mm, respectively. Signal waveforms are collected using a data acquisition system. Off-line data processing was used to obtain the neutron time-of-flight spectra and transmissions. The uncertainty of the counting statistics is generally approximately 3% for each bin in the energy range of 1–20 MeV. It is determined that the results for the neutron total cross section of carbon obtained using ^235U cells are in good agreement with the results obtained using 238U cells within limits of statistical uncertainty. Moreover, the measured total cross sections show good agreement with the broadening evaluated data.
基金Supported by the National Key Research and Development Plan(2016YFA0401603)the National Natural Science Foundation of China(11675155,11790321)Foundation of President of China Academy of Engineering Physics(YZJLX2016003)。
文摘The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power installations.The neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer(NTOX)based on the multi-cell fast fission chamber at the China Spallation Neutron Source(CSNS)-Back-n white neutron source(Back-n).The fission count-neutron energy distributions of ^(235)U and ^(238)U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW.The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV.The neutron total cross section of^(9)Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region.In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV,the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5%and 15%,respectively.In the resonance energy region,the measured resonance energies in our experiment were 0.63,0.82,and 2.8 MeV,respectively.The results showed that the total cross section uncertainties of three Be samples were within 2.2%in the energy region below 1 MeV.The total cross section uncertainty of 30 mm Be from ^(235)U was the smallest and less than 5%in the energy region of 0.3 eV−120 MeV.The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.
基金This work was supported by the National Natural Sci-ence Foundation of China under Grant No. 10174019
文摘Total cross sections （TCSs） of electrons scattering from triatomic molecules over the energy range from 30 to 5000 eV are investigated employing a new semi-empirical formula. The TCSs of electrons scattering from triatomic molecules SO2, NO2, and CO2 are calculated. The quantitative TCSs are in good agreement with those obtained by experiments. It is shown that the results derived from the semi-empirical formula are much closer to the measurements than other calculations.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 10574039.
文摘The total （elastic plus inelastic） cross sections for positron scattering from N2 and CO2 over the incident energy range from 30 to 3000eV are calculated using the additivity rule model at Hartree-Fock level. A complex optical model potential modified by incorporating the concept of bonded atom, which takes into account the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross section of positron-molecule scattering. The calculated total cross sections are in good agreement with those reported by experiments and other theories over a wide energy range.
基金the National Natural Science Foundation of China(Grant Nos.11934004 and U1832201)the Science Challenge Project(Grant No.TZ2016005)the CAEP Foundation(Grant No.CX2019022).
文摘The electron-impact ionization of lithium-like ions C^(3+),N^(4+),O^(5+),Ne^(7+),and Fe2^(3+)is studied using a combination of two-potential distorted-wave and R-matrix methods with a relativistic correction.Total cross sections are computed for incident energies from 1 to 10 times of ionization energy and better agreements with the experimental results are obtained in comparison with the theoretical data available.It is found that the indirect ionization processes become significant for the incident energy larger than about four times of the ionization energy.Contributions from the exchange effects along the isoelectronic sequence are also discussed and found to be important.The present method can be used to obtain systematic ionization cross sections for highly charged ions across a wide incident energy range.
基金Supported by the National Natural Science Foundation of China under Grant No.10547005
文摘By using the nuclear reaction model for light nuclei, the calculations of the double-differential cross sections of outgoing neutrons from n ＋^9Be reactions are performed. The total outgoing neutrons are only come from the （n, 2n）2a reaction channel. The （n, 2n）2a reaction channel is achieved through six different reaction approach, which are illustrated in this paper. The calculated results agree very well with the measured data at En = 7.1, 8.09, 8.17, 9.09, 9.97 and 10.26 MeV, because the updated level schemes related to the n ＋ ^9Be reactions have been employed in this calculations.
文摘In this work, the elastic cross section is calculated at energies above the Coulomb barrier for 3He + 58Ni using a Woods-Saxon potential. The solutions of the radial Schrödinger equations are calculated numerically and they are introduced in the S matrix, after which the cross section is obtained. The parameters in the potential are adjusted to satisfy known experimental data.
文摘We demonstrate a new technique for calculating proton-proton inelastic cross-section, which allows one by application of the Laplace' method replace the integrand in the integral for the scattering amplitude in the vicinity of the maximum point by expression of Gaussian type. This, in turn, allows us to overcome the computational difficulties for the calculation of the integrals expressing the cross section to sufficiently large numbers of particles. We have managed to overcome these problems in calculating the proton-proton inelastic cross-section for production (n ≤ 8) number of secondary particles in within the framework of φ3 model. As the result the obtained dependence of inelastic cross-section and total scattering cross-section on the energy √s are qualitative agrees with the experimental data. Such description of total cross-section behavior differs considerably from existing now description, where reggeons exchange with the intercept greater than unity is considered.
文摘We demonstrate a possibility of computation of inelastic scattering cross-section in a multi-peripheral model by application of the Laplace method to multidimensional integral over the domain of physical process. Founded the constrained maximum point of scattering cross-section integral under condition of the energy-momentum conservation. The integrand is substituted for an expression of Gaussian type in the neighborhood of this point. It made possible to compute this integral numerically. The paper has two parts. The hunting procedure of the constrained maximum point is considered and the properties of this maximum point are discussed in the given part of the paper. It is shown that virtuality of all internal lines of the “comb” diagram reduced at the constrained maximum point with energy growth. In the second part of the paper we give some the arguments in favor of consideration of the mechanism of virtuality reduction as the mechanism of the total hadron scattering cross-section growth, which is not taken into account within the framework of Regge theory.
