A new R-matrix approach for calculating cross sections and rate coefficients electron-impact excitation of complex atoms ions is described. This approach, based on an expansion the total wavefunction in target configurations rather than individual states taking advantage special status scattered electron collisional wavefunction, enables angular integrals to be performed very much more efficiently hitherto. It also correlation effects electron-target collision treated consistently,...

Close coupling calculations of line shape parameters have been performed for the first pure rotational R0(j = 0-4) lines CO in helium baths at various temperatures. Besides usual Lorentzian widths and shifts, we provide complex Dicke as well double power law temperature representation all four parameters. In addition, study speed dependence these The R0(0) R0(1) theoretical thermally averaged collisional shifts between 500 about 15 K are excellent agreement with values reported literature....

Total cross sections for single electron capture, ionization, resonant double capture and transfer ionization processes during the collision of H+, He2+ nuclei with helium are calculated within continuum distorted wave approximation energy range 100-1600 keV amu-1. The semiclassical independent-event model is adopted, while effect correlation in atom explicitly accounted by use a two-electron ground state developed Pluvinage (1950). For all but lowest energies considered, results typically...

The target continuum distorted wave (TCDW) theory is derived and developed. It describes charge exchange in asymmetric collisions, particular the collision of a projectile ion low with high charge. final state represented by TCDW function. initial taken as travelling atomic orbital, while intermediate states are Coulomb-Green applied to capture protons from inner shells heavy atoms. For s-s transitions, it found that within standard on-shell full-peaking approximation second-order amplitude...

A time-dependent method is used to calculate reaction probabilities for J = 0 C(1D) + H2 (v 0, j 0) → CH(v′, j′) H and S(1D) SH (v′, indirect reactive collisions. The state-to-state are dominated by a strong resonance structure associated with the formation of long-lived triatomic complex during collision. We compare our results those obtained using time-independent hyperspherical coordinates method. agreement very good: in particular, narrow resonances wave packet correspond exactly results.

Free–free transitions during the scattering of electrons by helium in presence a linearly polarized CO2 laser field are investigated both experimentally and theoretically. Signals for laser-assisted at 22 eV with absorption or emission up to two photons measured angles between 20° 70°, compared values obtained from an 11-state R-matrix Floquet calculation low-frequency approximation Kroll Watson. The sets theoretical results found be very good agreement geometries considered experiment....

The R-matrix Floquet theory is applied to the study of electron - hydrogen scattering in presence a laser field. One-electron models are first considered which target represented by potential. Results also presented for an explicit two-electron calculation, including 1s, and orbitals hydrogen. Angular distributions fairly good agreement with those low-frequency approximation, even when momentum transfer almost perpendicular polarization

Schwartz interpolation is used to derive grid representations particularly adapted problems involving the Coulomb potential. Bound state energies, expectation values and radial dipole moments for hydrogen atom are all reproduced high accuracy.

A new version of the R-matrix Floquet theory for laser-assisted electron-atom scattering is presented. The non-perturbative and applicable to a non-relativistic many-electron atom or ion in homogeneous linearly polarized field. It based on use channel functions built from field-dressed target states, which greatly simplifies general formalism.

The scattering of low-energy electrons by helium in the presence a CO2 laser field is studied using R-matrix Floquet theory. Two target states are retained calculations, 1S ground state and 1Po pseudostate optimized to describe polarizability target. Differential cross sections for elastic with net absorption/emission up two photons calculated collision energies between 1 eV 8 over range intensities from 107 W cm−2 108 cm−2. Various geometries considered, including those which incident...

Absolute total, partial, and differential cross sections for the photodetachment of oxygen anion are reported photon energies ranging from threshold (1.46 eV) to 5.5 eV. The total section was measured using animated-crossed-beam technique while partial were obtained velocity map imaging. values in good agreement with theoretical results an $R$-matrix calculation polarized pseudostates.

Using the R-matrix Floquet approach, we investigate two-photon emission of a 2p electron from 1s22s22p5 ground-state Ne+ irradiated by laser light with photon energies between 25 eV and 40 an intensity 1014 W cm−2. We obtain rates for initially in M = 0 1 levels. Two-photon level leaves Ne2+ predominantly 2p41De, whereas 2p43Pe. In sequential double ionization Ne, first step thus has noticeable influence on second step. The present differ significantly deduced experiment. main reason this is...

The R-matrix Floquet method is used to study electron-impact excitation of helium in the presence a CO 2 laser field, for collision energies between 19 and 21.5 eV intensities 10 7 8 W cm -2 .Collision geometries with electron incident at various angles polarization axis are considered.The signal production metastable states good agreement results low-frequency approximation semi-classical approach, while experiment reasonable.

The R-matrix method is used to investigate electron-impact excitation of neutral carbon over an energy range interest for fusion plasma modelling. Two independent calculations are carried out. In the first, all levels with included in expansion total wavefunction and cross sections including exchange calculated collision energies from threshold 150 eV. second, spin-allowed excluding 60 Cross effective strengths presented important transitions.

The two-dimensional R-matrix propagator of Le Dourneuf et al. [J. Phys. B 23, L559 (1990)] is generalized to arbitrary angular momenta and applied the study electron-hydrogen collisions at energies up n=5 threshold. Results are presented for phase shifts, resonance positions widths, as well cross sections partial waves total L\ensuremath{\le}3. stability efficiency method established. A comparison made below n=3 threshold with results from other theories. Agreement very good, in particular a...

The R-matrix Floquet method is used to study electron-helium scattering in a Nd-YAG laser the energy range from 0.65 0.78 Hartree. effect of strong AC Stark mixing between 1s2s 3S and 1s2p 3Po states discussed. Integrated cross sections for elastic excitation ground state into triplet are presented. He-(1s2s2 2S) resonance shown be dominant feature below field-free threshold.

The first-order boundary-corrected Born (B1B) and target continuum distorted-wave (TCDW1) theories are used to calculate differential total cross sections for K-shell capture various fast asymmetric collisions. It is found that B1B do not peak, those TCDW1 more sensitive the choice of binding energy. For displays an unphysical dip, whereas follows experimental data well. concluded a one-channel theory provides reasonable approach study these

The lifetime matrix is used to investigate shape resonances in electron-hydrogen scattering above the n = 2, 3 and 4 thresholds. calculated positions widths of these are generally good agreement with values obtained by other methods, notably those based on complex coordinate rotation.

By considering the target continuum distorted-wave (TCDW) theory as high-energy limit of half-way house variational theory, it is shown not only that there no intermediate elastic divergence but also second-order amplitude based on a purely state order v-6 and thus negligible. The residual inelastic TCDW developed to at high velocities. It used describe charge exchange during collisions fast protons with atomic hydrogen. Using an on-shell peaking approximation 1s-1s capture transition...

Cross sections for one- and two-photon detachment of ${\mathrm{O}}^{\ensuremath{-}}(1{s}^{2}2{s}^{2}2{p}^{5}\phantom{\rule{0.16em}{0ex}}^{2}\mathrm{P}^{\mathrm{o}})$ have been determined in a joint experimental theoretical study. The absolute measurement is based on the animated-crossed-beam technique, which extended to case pulsed lasers, ion beams, multiphoton detachment. ab initio calculations employ $R$-matrix Floquet theory, with simple descriptions initial bound state residual oxygen...

General selection rules for differential cross sections laser-assisted electron-atom scattering are derived the geometry in which linearly polarized laser field is perpendicular to plane. Numerical calculations using $R$-matrix Floquet theory presented electron-helium order discuss possibility of observing these experimentally.

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Electron-impact excitation of the ground state hydrogen into states is studied by propagating R-matrix in two radial dimensions. Integral cross sections and resonance parameters are presented for collision energies from 0.75 Ryd (the n = 2 threshold) up to 0.96 5 threshold). Below 3 threshold, there very good agreement with results other methods experimental data. Between 4 thresholds, integral better those a coupled pseudostate method than J-matrix method, while 15-state calculation.