scholarly journals Photoionisation and Auger Electron Emission from the Lithium Molecule: Calculations using Multicentre Numerical Continuum Functions

1986 ◽  
Vol 39 (5) ◽  
pp. 809 ◽  
Author(s):  
FP Larkins ◽  
JA Richards
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Electron Emission ◽  
First Principles ◽  
Transition Rates ◽  
Hartree Fock ◽  
Photoemission Data ◽  
Experimental Findings ◽  
Asymmetry Parameters ◽  
The Continuum

A numerical method has been used for the generation of molecular continuum wavefunctions at the relaxed Hartree-Fock level associated with the photoionisation of the lithium molecule. Exchange between the continuum electron and the ion core is included, but L coupling is neglected. Cross sections for core and valence shell photoionisation have been calculated from threshold to 6�0 a. u. The results differ significantly in detail from previous multiple scattering calculations. Continuum phase shifts and the asymmetry parameters for the various processes are also reported. The molecular cross section values are compared with atomic cross sections calculated at the relaxed Hartree-Fock level. The Li2 molecular Auger transition rates are also calculated from first principles using the appropriate two-centre continuum functions. The results provide a basis for the reinterpretation of recent experimental findings of photoemission data for the lithium vapour system.

Untersuchungen zur Wirkung von monochromatischer Vakuum-UV-Strahlung auf DNS

1969 ◽  
Vol 24 (6) ◽  
pp. 722-728 ◽  
Author(s):  
K. U. Berger
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Electron Emission ◽  
Vacuum Ultraviolet ◽  
Monochromatic Light ◽  
Ionization Probability ◽  
Thin Layers ◽  
Inactivation Mechanism ◽  
Grating Monochromator ◽  
Vacuum Uv

Inactivation cross sections of infectious ΦΧ-174-DNA in the extreme vacuum-ultraviolet were determined by irradiation of thin layers with monochromatic light down to 584 Å by means of a powerful grating-monochromator, the elements of which are described. Comparison of inactivation and light-induced electron emission shows that light of quantum energies below 7 eV inactivates by excitation only, whereas above 10.2 eV ionization is the predominant inactivation mechanism. Because of the satisfactory agreement of the curves for inactivation and electron emission, it is conducted that the remarkable increase of the inactivation cross section in the region of the short wavelength vacuum-uv is due to increasing ionization probability.

Cross section for the excitation of helium by protons

1979 ◽  
Vol 57 (8) ◽  
pp. 1174-1177
Author(s):  
S. P. Ojha ◽  
P. Tiwari
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Proton Impact ◽  
Experimental Findings

Cross sections for the singlet excitation of helium by proton impact have been computed using the Vainshtein, Presnyakov, and Sobelman (VPS) method with peaking approximation. Transitions from the ground state to the n1P(n = 2, 3, and 4) states have been taken into account. The results are compared with other theoretical and experimental findings.

A GTO basis set calculation of properties of the continuum. Photoionization and resonances of He

1992 ◽  
Vol 70 (2) ◽  
pp. 513-519 ◽  
Author(s):  
Roberto Moccia ◽  
Pietro Spizzo
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Photoionization Cross Section ◽  
Basis Set ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Continuum States ◽  
K Matrix ◽  
The Continuum ◽  
Autoionizing States

By using the K-matrix technique for the continuum states that was previously employed with particularly diffuse L2 basis sets, it is shown that GTO bases are also capable of yielding accurate values for the properties belonging to the electronic continuum. The method has been tested for helium and proved of satisfactory accuracy also for the analysis of the autoionizing states. The results include the phase shifts of the continuum states of the 1Seand 1P° manifolds, the properties of the lowest resonances of these symmetries, the ground state photoionization cross section, and the S contribution to the 1s2p1P° photoionization cross section. The results obtained suggest that the proposed technique should be useful for computing molecular differential photoionization cross sections by exploiting the widely used codes that employ GTO bases. Keywords: photoionization, Gaussian basis sets, helium, autoionizing states.

Spin-Dependence of the Electron Scattering Cross Section by a Magnetic Layer System and the Magneto-Resistance

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3376-3380 ◽  
Author(s):  
J. T. Wang ◽  
F. Tang ◽  
W. D. Brown ◽  
D. Bagayoko
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Magnetic Layer ◽  
Bulk Sample ◽  
Scattering Cross Section ◽  
Layer System ◽  
Interfacial Roughness ◽  
Scattering Cross ◽  
Experimental Findings ◽  
Magneto Resistance

We present a theoretical model for calculating the spin-dependent cross section of the scattering of electrons by a magnetic layer system. Our model demonstrates that the cross sections of the scattering are different for spin up and spin down electrons. The model assumes that the electrical resistivity in a conductor is proportional to the scattering cross section of the electron in it. It is believed to support the two channel mechanism in interpreting magneto-resistance (MR). Based on the model without considering the scattering due to the interfacial roughness and the spin flipping scattering, we have established a relationship between MR and the square of the magnetic moment in the bulk sample without considering the scattering due to the interfacial roughness and the spin flipping scattering. It can also qualitatively explain the MR difference between the current in plane (CIP) and current perpendicular to the plane (CPP) configurations. The predictions by the model agree well with the experimental findings.

Discrete versus continuum relaxation modes of a hard sphere gas

1984 ◽  
Vol 62 (2) ◽  
pp. 97-103 ◽  
Author(s):  
Bernard Shizgal
Keyword(s):  
Discrete Spectrum ◽  
Cross Section ◽  
Cross Sections ◽  
Hard Sphere ◽  
Expansion Method ◽  
Gas Mixture ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate ◽  
Relaxation Modes ◽  
The Continuum

The nature of the discrete spectrum of the linear Boltzmann collision operators for a simple gas and for a gas mixture is studied numerically with a discrete ordinate method. The discrete ordinate method is found to give a large number of discrete eigenvalues whereas the expansion method with Burnett functions yields only a few converged eigenvalues. The hard sphere cross section is used in the present paper although the methods employed are readily applicable to other cross sections. The approach of the eigenvalues to the continuum boundary is studied in detail and a comparison with a previous asymptotic Wentzell–Kramers–Brillouin (WKB) analysis yields excellent agreement.

Many-Electron Correlations in the Photoionization of a Nitrogen Atom

1974 ◽  
Vol 52 (4) ◽  
pp. 349-354 ◽  
Author(s):  
N. A. Cherepkov ◽  
L. V. Chernysheva ◽  
V. Radojević ◽  
I. Pavlin
Keyword(s):  
Nitrogen Atom ◽  
Cross Section ◽  
Cross Sections ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Electron Correlations ◽  
Sum Rule ◽  
Hartree Fock ◽  
The Cross ◽  
Good Agreement

Photoionization cross sections for the outer shell of the nitrogen atom ground state are calculated in the single-particle Hartree–Fock approximation and, in order to take into account many-electron correlations, also in the Random Phase Approximation with Exchange (RPAE). To be able to apply the RPAE, its modification for the half-filled shell atom, such as nitrogen atom, is presented. Calculation of length and velocity forms of the cross section in both approximations are compared with the available experimental data, and a good agreement is obtained. It has been found that in the RPAE the influence of many-electron correlations in a nitrogen atom is not great, but it is very important since, in contrast to the Hartree–Fock approximation, it results in the validity of the sum rule and the coincidence of the length and velocity forms of the cross sections, in agreement with the requirement of the general theory. The angular distribution of photoelectrons is also calculated in the RPAE, which has not been measured so far.

scholarly journals Electron scattering cross-sections for particle transport modeling in a weakly ionized air plasma

2021 ◽  
Vol 51 ◽  
pp. 96-111
Author(s):  
Vasily Sergeevich Zakharov ◽  
Mikhail Evgenievich Zhukovskiy ◽  
Sergey Vasilievich Zakharov ◽  
Mikhail Borisovich Markov
Keyword(s):  
Elastic Scattering ◽  
Cross Section ◽  
Electron Scattering ◽  
Cross Sections ◽  
Electron Interaction ◽  
Inelastic Electron ◽  
Neutral Atoms ◽  
Hartree Fock ◽  
Wide Range ◽  
The Cross

Data on processes of electron scattering on ions and neutral atoms are required in fundamental studies and in applied research in such fields as astro- and laser physics, low density plasma simulations, kinetic modeling etc. Experimental and computational data on elastic and inelastic electron scattering in a wide range of electron energies is available mostly for the electron interaction with neutral atoms, but are very limited for the scattering on ions, notably for elastic processes. In present work the calculational approaches for the cross-section computation of electron elastic and inelastic scattering on neutral atoms and ions are considered. The atomic and ion properties obtained in quantum-statistical Hartree-Fock-Slater model are used in the direct computation of electron elastic scattering and ionization cross-sections by a partial waves method, semiclassical and distorted-wave approximations. Calculated cross-sections for elastic scattering on nitrogen and oxygen atoms and ions, and electron ionisation cross-sections are compared with the available experimental data and widely used approximations and propose consistent results. Considering applicability of Hartree-Fock-Slater model in wide scope of temperatures and densities, such approach to the cross-section calculation can be used in a broad range of energies and ion charges.

scholarly journals VUV-absorption cross section of carbon dioxide from 150 to 800 K and applications to warm exoplanetary atmospheres

2018 ◽  
Vol 609 ◽  
pp. A34 ◽  
Author(s):  
O. Venot ◽  
Y. Bénilan ◽  
N. Fray ◽  
M.-C. Gazeau ◽  
F. Lefèvre ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
High Resolution ◽  
Cross Section ◽  
Wavelength Range ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Planetary Atmospheres ◽  
Temperature Dependency ◽  
Absorption Cross ◽  
The Continuum

Context. Most exoplanets detected so far have atmospheric temperatures significantly higher than 300 K. Often close to their star, they receive an intense UV photons flux that triggers important photodissociation processes. The temperature dependency of vacuum ultraviolet (VUV) absorption cross sections are poorly known, leading to an undefined uncertainty in atmospheric models. Similarly, data measured at low temperatures similar to those of the high atmosphere of Mars, Venus, and Titan are often lacking. Aims. Our aim is to quantify the temperature dependency of the VUV absorption cross sections of important molecules in planetary atmospheres. We want to provide high-resolution data at temperatures prevailing in these media, and a simple parameterisation of the absorption in order to simplify its use in photochemical models. This study focuses on carbon dioxide (CO2). Methods. We performed experimental measurements of CO2 absorption cross sections with synchrotron radiation for the wavelength range (115–200 nm). For longer wavelengths (195–230 nm), we used a deuterium lamp and a 1.5 m Jobin-Yvon spectrometer. We used these data in our one-dimensional (1D) thermo-photochemical model in order to study their impact on the predicted atmospheric compositions. Results. The VUV absorption cross section of CO2 increases with the temperature. The absorption we measured at 150 K seems to be close to the absorption of CO2 in the fundamental ground state. The absorption cross section can be separated into two parts: a continuum and a fine structure superimposed on the continuum. The variation in the continuum of absorption can be represented by the sum of three Gaussian functions. Using data at high temperature in thermo-photochemical models significantly modifies the abundance and the photodissociation rates of many species in addition to CO2, such as methane and ammonia. These deviations have an impact on synthetic transmission spectra, leading to variations of up to 5 ppm. Conclusions. We present a full set of high-resolution (Δλ = 0.03 nm) absorption cross sections of CO2 from 115 to 230 nm for temperatures ranging from 150 to 800 K. A parameterisation allows us to calculate the continuum of absorption in this wavelength range. Extrapolation at higher temperature has not been validated experimentally and therefore should be used with caution. Similar studies on other major species are necessary to improve our understanding of planetary atmospheres.

Discrepancy of in-medium nucleon–nucleon cross-section in different T-matrix representations

2014 ◽  
Vol 23 (04) ◽  
pp. 1450023 ◽  
Author(s):  
Yong-Zhong Xing ◽  
Xing-Wen Zhao
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Nucleon Nucleon ◽  
Matrix Representations ◽  
Proton Proton ◽  
Hartree Fock ◽  
Wave States ◽  
T Matrix ◽  
The Cross ◽  
Three Body

In this paper, we study the in-medium nucleon–nucleon (NN) cross-section by using the Dirac–Breuckner–Hartree–Fock approximation (DBHF) with T-matrix project technique for determining the nucleon self-energy. By solving Thompson equation for different partial-wave states separately, we find that the discrepancies of nucleon self-energies in various T-matrix project representations are dominated by the channels with smaller angular momentum. Although the cross-section is independent on the project of T-matrix, the medium suppression of the cross-section in various T-matrix representations are apparently different due to the self-consistency of DBHF calculation involving effect mass of nucleon as an iterative parameter. Our results also show that the cross-sections in the complete pseudovector (CPV) choices are larger than those obtained with both DBHF in the pseudoscalar (PS) choice and nonrelativistic Brueckner–Hartree–Fock with three-body force (BHF + 3BF), respectively. Further comparison shows that the neutron–proton (NP) cross-section within DBHF + PV approach, [Formula: see text], is approximately equal to and slightly larger than that evaluated with BHF + 3BF, [Formula: see text], while the neutron–neutron (NN) (or proton–proton (PP)) cross-section given by DBHF + PV method, [Formula: see text], being the closest to the cross-section calculated by using BHF without 3BF in the lower energy region. Additionally, the discrepancies of the in-medium nucleon–nucleon differential cross-section induced by different representations of T-matrix in DBHF are discussed for nuclear matter with different densities.

Notes on the Kinematics of an Octopus’s Arm

2008 ◽  
Author(s):  
Y. Levinson ◽  
R. Segev ◽  
A. Shapiro
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Discrete Model ◽  
Continuum Model ◽  
Plane Deformation ◽  
Point Of View ◽  
Parallel Mechanisms ◽  
Rod Model ◽  
The Cross ◽  
The Continuum

In a study of the kinematics of an Octopus’s arm from the robotics point of view, we consider two models: a discrete model and a continuum model. Both models represent control of the curve in space defined by the centerline of the arm and the position of the suction elements of the arm relative to the centerline. The two models also represent the control of the arm by means of three groups of muscles: the longitudinal, transverse and helicoidal groups. Another feature of the kinematics exhibited by the two models is the use of incompressibility in the control of the arm. In the discrete model, the arm is represented as a sequence of parallel mechanisms. Each mechanism in the sequence consists of two parallel platforms of variable dimensions so that the resulting sequence of platforms represents the various cross sections of the arm. The continuum rod model that we use allows linear in-plane deformation of the cross-section and assumes that cross-sections remain perpendicular to the axis of the rod.

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