Evidence of initial-state two-center effects for (e, 2e) reactions

Coincidence, or (e, 2e), measurements of electron-impact ionization of atoms have established that the largest values of triply differential cross sections are obtained in collisions involving small momentum transfer to the target. Absolute measurements for these reactions are now available for hydrogen at 54.4-eV impact energy, and relative data have recently been reported at 27.2 eV. Previous theoretical works have concentrated on employing asymptotically correct two-center wave functions for the final state, leaving the initial state described by the Born approximation. Here we report results for which asymptotically correct two-center wave functions are used for both the initial and final states of the scattering system. Comparison of these results with experiment reveals that two-center effects (projectile-target correlations) are also important in the initial state

Coherent excitation of the singlet-triplet mixed 1s4f state of helium

In this paper, we present a detailed theoretical description for the coherent electron-impact excitation, the subsequent time evolution, and the cascading decay process of the singlet-triplet mixed 1s4f state of helium. The excitation amplitude and phase of each sublevel of this state are related to measurable coincidence intensities and polarizations of the emitted photons. It is found that the intensity and polarization of the emitted photons are time modulated due to the singlet and triplet mixing in the 1s4f state

Single ionization of helium by 102 eV electron impact: three-dimensional images for electron emission

Single ionization of helium by 102 eV electron impact has been studied by measuring the momentum vectors of all final-state particles, i.e., two electrons and the He + ion, with an advanced reaction microscope. Fully differential cross sections for asymmetric scattering geometry, which have been normalized to an absolute scale, have been obtained covering a large range of emission angles for the emitted low-energy (E ≤ 15 eV) electron and different scattering angles for the fast electron. Strong electron emission out of the projectile scattering plane is confirmed for electron impact, as was observed before for heavy-ion impact ionization. The data are compared with theoretical predictions from a three-Coulomb wavefunction model, first-order and second-order distorted-wave approaches, as well as a convergent close-coupling calculation

Resonance Effects in the Nonadiabatic Nonlinear Quantum Dimer

The quantum nonlinear dimer consisting of an electron shuttling between the two sites and in weak interaction with vibrations, is studied numerically under the application of a DC electric field. A field-induced resonance phenomenon between the vibrations and the electronic oscillations is found to influence the electronic transport greatly. For initially delocalization of the electron, the resonance has the effect of a dramatic increase in the transport. Nonlinear frequency mixing is identified as the main mechanism that influences transport. A characterization of the frequency spectrum is also presented.Comment: 7 pages, 6 figure

Coherence analysis of the He 1s4f state

Theoretical calculations of the Stokes parameters were performed for the 3 1D→2 1P transition in the decay of the 1s4f state of helium. Three different distorted-wave calculations were compared with the measurements of Cvejanovic and Crow and reasonable agreement was found for all three models. Overall, the ground state potential model was in good agreement with the data than the other two models. However, it is difficult to make a distinction between the theories due to the size of the error bars and the similarity of the theoretical results

Role of electron-electron correlation in (e,2e) reactions

For the last several years, there has been significant attention paid to examining the role of final state correlation in (e,2e) collisions. Numerous calculations have been performed using wavefunctions that not only are asymptotically correct but that were also designed to incorporate other final state physical effects. While these elaborate wavefunctions gave improved agreement with experiment in some cases, none were consistently better than the original three coulomb wavefunction of Redmond, which was used by Brauner, Briggs and Klar in 1989. In al1 of these calculations, initial state correlation were ignored. In this paper, we will report on the importance of initial state correlation on the (e,2e) scattering process