scholarly journals Multi-photon above threshold ionization of multi-electron atoms and molecules using the R-matrix approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jakub Benda ◽  
Zdeněk Mašín
Keyword(s):  
Cross Sections ◽  
Outer Region ◽  
Angular Distributions ◽  
Matrix Formalism ◽  
Computationally Efficient ◽  
Threshold Ionization ◽  
R Matrix ◽  
Atoms And Molecules ◽  
Above Threshold Ionization ◽  
Transition Matrix Elements

AbstractWe formulate a computationally efficient time-independent method based on the multi-electron molecular R-matrix formalism. This method is used to calculate transition matrix elements for the multi-photon ionization of atoms and molecules under the influence of a perturbative field. The method relies on the partitioning of space which allows us to calculate the infinite-range free-free dipole integrals analytically in the outer region, beyond the range of the initial bound wave function. This approach is valid for an arbitrary order, that is, any number of photons absorbed both in the bound and the continuum part of the spectrum (below- and above-threshold ionization). We calculate generalized multi-photon cross sections and angular distributions of different systems (H, He, $$\hbox {H}_{{2}}$$ H 2 , $$\hbox {CO}_{{2}}$$ CO 2 ) and validate our approach by comparison with data from the literature.

scholarly journals Above-threshold ionization of hydrogen and hydrogen-like ions by X-ray pulses

Open Physics ◽  
2013 ◽  
Vol 11 (9) ◽  
Author(s):  
Henri Bachau ◽  
Olimpia Budriga ◽  
Mihai Dondera ◽  
Viorica Florescu
Keyword(s):  
Plane Wave ◽  
Cross Sections ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Relativistic Effects ◽  
Electron Interaction ◽  
Radial Coordinate ◽  
Threshold Ionization ◽  
X Ray ◽  
Above Threshold Ionization

AbstractThis paper adresses the problem of above-threshold ionization (ATI) of hydrogen interacting with an intense X-ray electromagnetic field. Two approaches have been used. In the first approach, we calculate generalized differential and total cross sections based on second-order perturbation theory for the electron interaction with a monochromatic plane wave, with the A 2 and A · P contributions from the nonrelativistic Hamiltonian (including retardation) treated exactly. In the second approach, we solve the time-dependent Schrödinger equation (TDSE) for a pulsed plane wave using a spectral approach with a basis of oneelectron orbitals, calculated with L 2-integrable B-spline functions for the radial coordinate and spherical harmonics Y lm for the angular part. Retardation effects are included up to O(1/c), they induce extra terms forcing the resolution of the TDSE in a three dimensional space. Relativistic effects [of O (1/c 2)] are fully neglected. The isoelectronic series of hydrogen is explored in the range Z = 1 − 5 in both TDSE and perturbative approaches. Photoelectron angular distributions are obtained for photon energies of 1 keV and 3 keV for hydrogen, and photon energy of 25 keV for the hydrogenic ion B4+. Perturbative and TDSE calculations are compared.

scholarly journals ELASTIC BACKSCATTERED CROSS-SECTIONS OF 14N(P,P0)14N AT HIGH ANGLES

2020 ◽  
Vol 20 (3) ◽  
pp. 749-754
Author(s):  
MOHAMED ELTAYEB M. EISA ◽  
JOHAN ANDRE MARS ◽  
MUSTAFA J. ABUALREISH ◽  
MARWA L. WAREGH
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ion Beam ◽  
Region Of Interest ◽  
Laboratory Frame ◽  
Matrix Formalism ◽  
Cross Section Data ◽  
R Matrix ◽  
Section Data ◽  
Elastic Backscattering

The importance and present needs of proton cross section data of nitrogen needed by the Ion Beam Analysis (IBA) community are briefly reviewed. Previous experimental data presently used for the theoretical determination of the proton cross-sections are discussed. The Azure code based on the R-matrix formalism was then used to evaluate the data and to determine the nitrogen cross section in the previous and presently desired angular domain and energy region of interest. The experimental elastic backscattering cross section data, as spectra, for back-scattering analysis determined at angles in the laboratory frame of reference, θi,lab, of 165o, 170o and 176o are presented.

scholarly journals Developments regarding three-body reaction channels within the R-matrix formalism

2020 ◽  
Vol 239 ◽  
pp. 03002
Author(s):  
Benedikt Raab ◽  
Thomas Srdinko ◽  
Helmut Leeb
Keyword(s):  
Cross Sections ◽  
Matrix Theory ◽  
Resonance Region ◽  
Reaction Cross ◽  
Resonance Structure ◽  
Matrix Formalism ◽  
Matrix Formulation ◽  
R Matrix ◽  
Reaction Channels ◽  
Three Body

At low incident energies of nucleon-induced reaction cross sections exhibit a striking resonance structure which cannot properly be described by (semi-) microscopic models. Usually R-matrix theory is applied which provides a sufficiently accurate but phenomenological description of the resonance region. However, standard R-matrix theory is only suited for two-particle channels. Three- and many-particle channels which may occur at rather low incident energies and are usually treated in approximative or effective way. In this contribution an extension to unequal masses of the R-matrix formulation of Glockle based on the Faddeev equation is performed and proper expressions for numerical implementation are given.

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