Showing papers on "Schwinger variational principle published in 2015"
TL;DR: The Schwinger multichannel method as discussed by the authors was designed to account for exchange, polarization and electronically multi-channel coupling effects in the low-energy region of electron scattering from molecules with arbitrary geometry.
Abstract: The Schwinger multichannel method [K. Takatsuka and V. McKoy, Phys. Rev. A 30, 1734 (1984)], which is based on the Schwinger variational principle for the scattering amplitude [J. Schwinger, Phys. Rev. 72, 742 (1947)], was designed to account for exchange, polarization and electronically multichannel coupling effects in the low-energy region of electron scattering from molecules with arbitrary geometry. The applications of the method became more ambitious with the availability of computer power combined with parallel processing, use of norm-conserving pseudopotentials and improvement of the description of target excited states (minimal orbital basis for single configuration interaction). The most recent applications involving 33 and 45 electronically open channels for phenol and ethylene molecules, represent good examples of the present status of the method. In this colloquium, we review the strategy and point out new directions to apply the method in its full extension.
98 citations
TL;DR: In this paper, the Schwinger variational approach was used to obtain the scattering parameters for different confining potentials symmetric in x,y, and the results showed the vanishing of the total photoabsorption probability ateverychannel threshold and the occurrence of resonances below the channel thresholds for negative scattering lengths.
Abstract: Atheoreticalmethodfortreatingcollisionsinthepresenceofmultiplepotentialsisdevelopedbyemployingthe Schwinger variational principle. The current treatment agrees with the local (regularized) frame transformation theory and extends its capabilities. Specifically, the Schwinger variational approach gives results without the divergences that need to be regularized in other methods. Furthermore, it provides a framework to identify the origin of these singularities and possibly improve the local frame transformation. We have used the method to obtain the scattering parameters for different confining potentials symmetric in x,y. The method is also used to treat photodetachment processes in the presence of various confining potentials, thereby highlighting effects of the infinitely many closed channels. Two general features predicted are the vanishing of the total photoabsorption probability ateverychannel threshold and the occurrence of resonances below the channel thresholds for negative scattering lengths. In addition, the case of negative-ion photodetachment in the presence of uniform magnetic fields is also considered where unique features emerge at large scattering lengths.
5 citations
07 Sep 2015
TL;DR: In this paper, the authors investigated the process of negative ion photodetachement in the presence of external fields by employing the theoretical framework of Schwinger variational principle and the local frame transformation theory.
Abstract: Processes of alkali-atom photoionization and negative ion photodetachement in the presence of external fields are investigated. The corresponding photoabsorption spectra are interpreted by employing the theoretical framework of Schwinger variational principle and the local frame transformation theory.