Polarization and correlation effects in elastic electron-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Li</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>scattering

Gil, T.J.; McCurdy, C. W.; Rescigno, T. N.; Lengsfield, Byron H.

doi:10.1103/physreva.47.255

Cited by 12 publications

(15 citation statements)

References 20 publications

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“…The Li2 dimer has very low-lying excited states and an ionization potential of only 5 eV [17]. Moreover, from our previous study [18), we know that the~X+ partial cross section has a pronounced minimum near O. l eV which is sensitive to polarization effects and that the static-exchange approximation grossly overestimates the cross section in the energy range below 1 eV. In the present calculation, we describe the Li2 molecule in its ground state by a selfconsistent field (SCF) wave function, which has the configuration 4p = lo.…”

Section: Electron-molecule Scattering Above the Ionization Threshold mentioning

confidence: 90%

Electron-Molecule Scattering above the Ionization Threshold

Rescigno

McCurdy

1994

Phys. Rev. Lett.

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%e show how to extend close-coupling calculations into the intermediate energy region without explicitly including a large number of inelastic channels. By discretizing the target continuum in a suitably chosen set of complex functions, we can construct convergent representations of a Feshbach optical potential that represents open inelastic channels including the ionization continuum.The method can be implemented for electron scattering by atomic or molecular targets with minimal modifications to existing electronic structure codes. The method is illustrated by applying it to e + Li& elastic scattering. PACS numbers: 34.80.GsThe close-coupling formalism is the centerpiece of timeindependent scattering theory and has formed the basis of most ab initio work on low-energy electron-atom and electron-molecule scattering. The essence of the method is an expansion of the total wave function, describing the composite target + projectile system, in a complete set of internal states of the target, including the continuum. Scattering information is extracted from an examination of the asymptotic behavior of the channel functions, which are the coefficients of the target eigenstates in the total wave function. Obviously, the complete set of target states must be truncated to finite size in actual computations, and the continuum states, if included, must be appropriately discretized. Some time ago [1] it was learned that, in the low energy region below the ionization threshold, convergence could be accelerated by including energy pseudostates above that threshold in the expansion, typically obtained by diagonalizing the target Hamiltonian in a basis of square-integrable (L2) functions.The intermediate energy region, extending from the ionization threshold to an energy of a few hundred eV presents a formidable challenge for ab initio theory. The infinity of open channels precludes us, even in principle, from writing down a wave function that describes all possible scattering events and is simply a reflection of the fact that the ionization problem persists as one of the fundamentally unsolved problems of atomic collision theory. Close-coupling expansions that include pseudostates, when extended to the intermediate energy region, typically encounter unphysical resonances near pseudostate thresholds [2], although their effect appears to diminish with increasing number of states [3]. As computer power has increased over the years, so has the number of target states that could be included in close-coupling expansions, allowing some exploration of their convergence properties. Recently, Bray and Stelbovics [4] demonstrated, quite convincingly, that the close-coupling method does in fact converge at intermediate energies if enough states are included in the expansion. By including up to thirty target states in calculations on e + H scattering, they found that the pseudoresonance behavior eventually disappears. The intermediate energy R-matrix method [5] offers a similar approach to the problem but has not been able to obtain conver...

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Section: Electron-molecule Scattering Above the Ionization Threshold mentioning

confidence: 90%

Electron-Molecule Scattering above the Ionization Threshold

Rescigno

McCurdy

1994

Phys. Rev. Lett.

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“…In order to understand the dynamics captured in the time delay measurements shown in Fig. 1, we compare these data with predicted delays calculated using an implementation [38][39][40][41][42][43][44][45][46] of the complex Kohn variational method [47][48][49][50][51][52][53] for photoionization [54][55][56][57][58][59][60][61][62][63] and electron-molecule scattering [64][65][66][67][68][69][70][71][72][73]. The two-photon molecular photoionization time delays (τ PI ) are calculated in two different levels of approximation and then averaged over molecular orientation and outgoing electron direction, consistent with the measurement scheme used in the experiment (see the Appendix).…”

Section: Observation Of Continuum Channel Coupling In Photoionizamentioning

confidence: 99%

Electron correlation effects in attosecond photoionization of CO2

et al. 2020

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A technique for measuring photoionization time delays with attosecond precision is combined with calculations of photoionization matrix elements to demonstrate how multielectron dynamics affect photoionization time delays in carbon dioxide. Electron correlation is observed to affect the time delays through two mechanisms: autoionization of molecular Rydberg states and accelerated escape from a continuum shape resonance.

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“…From Eqs. (11) and ( 17) it follows that we can write the particle part of the inelastic Green's function as…”

Section: The Inelastic Green's Functionmentioning

confidence: 99%

“…The numerical applications of Feshbach's theory on electron-molecule scattering reported so far, have been realised by projection of configuration interaction (CI) matrices [8,9] but have rarely gone beyond the uncorrelated Hartree-Fock level for the description of the target's ground state. The inclusion of correlated, i. e., multi-configurational target wavefunctions in this context presents a delicate problem [10,11].…”

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Dynamical Green’s function and an exact optical potential for electron-molecule scattering including nuclear dynamics

1999

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(April 9, 1999, acc. for publ. Phys. Rev. A, physics/9907050) We derive a rigorous optical potential for electron-molecule scattering including the effects of nuclear dynamics by extending the common many-body Green's function approach to optical potentials beyond the fixed-nuclei limit for molecular targets. Our formalism treats the projectile electron and the nuclear motion of the target molecule on the same footing whereby the dynamical optical potential rigorously accounts for the complex many-body nature of the scattering target. One central result of the present work is that the common fixed-nuclei optical potential is a valid adiabatic approximation to the dynamical optical potential even when projectile and nuclear motion are (nonadiabatically) coupled as long as the scattering energy is well below the electronic excitation thresholds of the target. For extremely low projectile velocities, however, when the cross sections are most sensitive to the scattering potential, we expect the influences of the nuclear dynamics on the optical potential to become relevant. For these cases, a systematic way to improve the adiabatic approximation to the dynamical optical potential is presented that yields non-local operators with respect to the nuclear coordinates. 34.80.Gs,34.10.+x

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Polarization and correlation effects in elastic electron-Li2scattering

Cited by 12 publications

References 20 publications

Electron-Molecule Scattering above the Ionization Threshold

Electron-Molecule Scattering above the Ionization Threshold

Electron correlation effects in attosecond photoionization of CO2

Dynamical Green’s function and an exact optical potential for electron-molecule scattering including nuclear dynamics

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