scholarly journals ∆SCF Dyson Orbitals and Pole Strengths from Natural Ionization Orbitals

2020 ◽  
Author(s):  
Hassan Harb ◽  
Hrant Hratchian
Keyword(s):  
Modeling And Simulation ◽  
Cross Section ◽  
Excellent Agreement ◽  
Cross Sections ◽  
Photoionization Cross Section ◽  
Theory Model ◽  
Numerical Calculations ◽  
Pole Strength ◽  
Scf Calculations ◽  
Propagator Theory

The calculation of photoionization cross-sections can play a key role in spectral assignments using modeling and simulation. In this work, we provide formal relationships between pole strengths, which are proportional to the photoionization cross-section, and terms related to the Natural Ionization Orbital model for Delta-SCF calculations. A set of numerical calculations using the developed models is carried out. Pole strength values computed using the two approaches developed for Delta-SCF calculations demonstrate excellent agreement with an electron propagator theory model.

scholarly journals ∆SCF Dyson Orbitals and Pole Strengths from Natural Ionization Orbitals

2020 ◽  
Author(s):  
Hassan Harb ◽  
Hrant Hratchian
Keyword(s):  
Modeling And Simulation ◽  
Cross Section ◽  
Excellent Agreement ◽  
Cross Sections ◽  
Photoionization Cross Section ◽  
Theory Model ◽  
Numerical Calculations ◽  
Pole Strength ◽  
Scf Calculations ◽  
Propagator Theory

The calculation of photoionization cross-sections can play a key role in spectral assignments using modeling and simulation. In this work, we provide formal relationships between pole strengths, which are proportional to the photoionization cross-section, and terms related to the Natural Ionization Orbital model for Delta-SCF calculations. A set of numerical calculations using the developed models is carried out. Pole strength values computed using the two approaches developed for Delta-SCF calculations demonstrate excellent agreement with an electron propagator theory model.

scholarly journals Photoionization Cross-Sections of Carbon-Like N+ Near the K-Edge (390–440 eV)

Atoms ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 27
Author(s):  
Jean-Paul Mosnier ◽  
Eugene T. Kennedy ◽  
Jean-Marc Bizau ◽  
Denis Cubaynes ◽  
Ségolène Guilbaud ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Cross Sections ◽  
Experimental Studies ◽  
Photoionization Cross Section ◽  
Theoretical Work ◽  
Rydberg Series ◽  
R Matrix ◽  
Resonance Strengths ◽  
Nitrogen Ion

High-resolution K-shell photoionization cross-sections for the C-like atomic nitrogen ion (N+) are reported in the 398 eV (31.15 Å) to 450 eV (27.55 Å) energy (wavelength) range. The results were obtained from absolute ion-yield measurements using the SOLEIL synchrotron radiation facility for spectral bandpasses of 65 meV or 250 meV. In the photon energy region 398–403 eV, 1s⟶2p autoionizing resonance states dominated the cross section spectrum. Analyses of the experimental profiles yielded resonance strengths and Auger widths. In the 415–440 eV photon region 1s⟶(1s2s22p2 4P)np and 1s⟶(1s2s22p2 2P)np resonances forming well-developed Rydberg series up n=7 and n=8 , respectively, were identified in both the single and double ionization spectra. Theoretical photoionization cross-section calculations, performed using the R-matrix plus pseudo-states (RMPS) method and the multiconfiguration Dirac-Fock (MCDF) approach were bench marked against these high-resolution experimental results. Comparison of the state-of-the-art theoretical work with the experimental studies allowed the identification of new resonance features. Resonance strengths, energies and Auger widths (where available) are compared quantitatively with the theoretical values. Contributions from excited metastable states of the N+ ions were carefully considered throughout.

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.

The absolute determination of extinction cross-sections by the use of an open resonator

1970 ◽  
Vol 315 (1521) ◽  
pp. 217-230 ◽  
Keyword(s):  
Cross Section ◽  
Excellent Agreement ◽  
Cross Sections ◽  
Incident Wave ◽  
Open Resonator ◽  
Extinction Cross Section ◽  
Microwave Frequencies ◽  
Quarter Wavelength ◽  
Total Scattering Cross Section

A new experimental technique for determining the extinction cross-section of an obstacle at microwave frequencies is described. This method does not involve the measurement of fields but requires only the determination of the Q -factor of an open resonator, which can be done very accurately. By measuring the Q -factor of the resonator with no obstacle present, and then with the obstacle in two different positions a quarter wavelength apart along the axis of the resonator, the extinction cross-section can be deduced. The methodis, however, restricted to a class of obstacles possessing reflexion symmetry in a plane perpendicular to the direction of propagation of the incident wave. Experimental results with brass spheres for which the absorption is negligible (and therefore the extinction cross-section is nearly equal to the total scattering cross-section), give excellent agreement with Mie’s theory. Results are also given for steel spheres.

scholarly journals Single photoionization of the Kr-like Rb ii ion in the photon energy range 22–46.0 eV

2019 ◽  
Vol 486 (1) ◽  
pp. 245-250 ◽  
Author(s):  
Brendan M McLaughlin ◽  
James F Babb
Keyword(s):  
Cross Section ◽  
Photon Energy ◽  
Cross Sections ◽  
Large Scale ◽  
Experimental Studies ◽  
Photoionization Cross Section ◽  
Theoretical Work ◽  
Matrix Approximation ◽  
Theoretical Cross Section ◽  
R Matrix

Abstract Single photoionization cross-sections for Kr-like Rb+ ions are reported in the energy (wavelength) range from 22 (564 Å) to 46 eV (270 Å). Theoretical cross-section calculations for this trans-Fe element are compared with measurements from the ASTRID radiation facility in Aarhus, Denmark and from the dual laser plasma technique, at respectively 40 and 35 meV FWHM energy resolution. In the photon energy region 22–32 eV the spectrum is dominated by excitation auto-ionizing resonance states. Above 32 eV the cross-section exhibits classic Fano window resonances features, which are analysed and discussed. Large-scale theoretical photoionization cross-section calculations, performed using a Dirac Coulomb R-matrix approximation are benchmarked against these high-resolution experimental results. Comparison of the theoretical work with the experimental studies allowed the identification of resonance features and their parameters in the spectra in addition to contributions from excited metastable states of the Rb+ ions.

scholarly journals Photoionization Cross Sections of Carbon-Like N+ near the K-Edge (390 eV - 440 eV)

2021 ◽  
Author(s):  
Jean-Paul Mosnier ◽  
Eugene T Kennedy ◽  
Jean-Marc Bizau ◽  
Denis Cubaynes ◽  
Ségolène Guilbaud ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Cross Sections ◽  
Experimental Studies ◽  
Photoionization Cross Section ◽  
Theoretical Work ◽  
Rydberg Series ◽  
R Matrix ◽  
Resonance Strengths ◽  
Nitrogen Ion

High-resolution K-shell photoionization cross-sections for the C-like atomic nitrogen ion (N+) are reported in the 398 eV (31.15 Å) to 450 eV (27.55 Å) energy (wavelength) range. The results were obtained from absolute ion-yield measurements using the SOLEIL synchrotron radiation facility for spectral bandpasses of 65 meV or 250 meV. In the photon energy region 398 eV - 403 eV, 1s⟶2p autoionizing resonance states dominated the cross section spectrum. Analyses of the experimental profiles yielded resonance strengths and Auger widths. In the 415 eV - 440 eV photon region 1s⟶1s2s22p2 4Pnp and 1s⟶1s2s22p2 2Pnp resonances forming well-developed Rydberg series up n=7 and n=8 , respectively, were identified in both the single and double ionization spectra. Theoretical photoionization cross-section calculations, performed using the R-matrix plus pseudo-states (RMPS) method and the multiconfiguration Dirac-Fock (MCDF) approach were bench marked against these high-resolution experimental results. Comparison of the state-of-the-art theoretical work with the experimental studies allowed the identification of new resonance features. Resonance strengths, energies and Auger widths (where available) are compared quantitatively with the theoretical values. Contributions from excited metastable states of the N+ ions were carefully considered throughout.

Binding energies and photoionization cross-sections of donor and acceptor impurities in inverted core/shell ellipsoidal quantum dots: Effects of magnetic field, ellipsoid anisotropy and impurity position

2019 ◽  
Vol 33 (13) ◽  
pp. 1950131 ◽  
Author(s):  
Lei Shi ◽  
Zu-Wei Yan
Keyword(s):  
Magnetic Field ◽  
Quantum Dot ◽  
Cross Section ◽  
Cross Sections ◽  
Applied Magnetic Field ◽  
Photoionization Cross Section ◽  
Binding Energies ◽  
Core Shell ◽  
Perturbation Approach ◽  
Donor And Acceptor

Within the framework of the effective-mass approximation and by using a variational and perturbation approach, the binding energies and photoionization cross-sections of donor and acceptor impurities in an inverted core/shell ellipsoidal spherical quantum dot under an applied magnetic field have been studied. We have calculated the binding energies of both donor and acceptor impurities as a function of the core and shell sizes and shapes with different impurity positions under the applied magnetic field. In addition, the corresponding photoionization cross-section is calculated. Our results show that the binding energy of the acceptor impurity is larger than that of the donor impurity, and both of them with different impurity positions and quantum ellipsoid anisotropies will exhibit a nonmonotonic change. The peak value of the photoionization cross-section will reach a maximum with the increasing ratio R1/R2. It is found that the applied magnetic field can be an effective means of enhancing the photoionization cross-section of an impurity state in such core/shell quantum dot system.

Binding energies and photoionization cross-sections of donor impurities in GaN/AlxGa1−xN spherical quantum dot under hydrostatic pressure

2020 ◽  
Vol 34 (14) ◽  
pp. 2050153
Author(s):  
Shuo Li ◽  
Lei Shi ◽  
Zu-Wei Yan
Keyword(s):  
Hydrostatic Pressure ◽  
Binding Energy ◽  
Quantum Dot ◽  
Cross Section ◽  
Cross Sections ◽  
Photoionization Cross Section ◽  
Binding Energies ◽  
Core Shell ◽  
Core Size ◽  
Shell Size

In this paper, the binding energy and photoionization cross-section of donor impurity state in [Formula: see text] quantum dot structure are studied theoretically by using variational method. The variation of binding energy and photoionization cross-section with core and shell sizes at different impurity locations under hydrostatic pressure is calculated numerically. The results show that the binding energy decreases monotonously with the core size at different impurity locations for [Formula: see text] core/shell quantum dot. In contrast, for the inverted core/shell quantum dot, the binding energy exhibits different trends with the increase of core size at different impurity locations. But the binding energy decreases monotonically with the shell size for both of them. Moreover, when the photon energy is approximately equal to the donor binding energy, the peak of the photoionization cross-section appears. There will be different peak shifts under different conditions, and its peak intensity increases with the increase of core and shell sizes. When the hydrostatic pressure is applied, the binding energy and the peak strength of the photoionization cross-section increase with the increase of the pressure.

scholarly journals Photoionization of the francium 7P3/2 state

2017 ◽  
Vol 95 (3) ◽  
pp. 234-237
Author(s):  
R. Collister ◽  
J. Zhang ◽  
M. Tandecki ◽  
S. Aubin ◽  
E. Gomez ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Optical Trap ◽  
Photoionization Cross Section ◽  
Magneto Optical Trap ◽  
Alkali Atoms ◽  
Simple Extrapolation ◽  
Photoionization Rate

We have measured the non-resonant photoionization cross section of the 7P3/2 state of francium for 442 nm light to be 20.8 ± 7.1 Mb. Atoms were irradiated in a magneto-optical trap, and we deduce the photoionization rate from the change in trap lifetime. The result is consistent with a simple extrapolation of known cross sections for other alkali atoms.

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