Recent advances in the application of the Schwinger multichannel method with pseudopotentials to electron-molecule collisions

Abstract

Abstract. The Schwinger multichannel method [K. 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.

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

“…For details of the terminology used in this figure, please refer to Ref. 60. The results for the two isomers are very similar.…”

“…shows the DCS's for 15, 20, 30, and 40 eV electron impact energy obtained with the Schwinger Multichannel method with pseudopotentials 60 at the one-channel static-exchangeplus-polarization level of approximation. For details of the terminology used in this figure, please refer to Ref.…”

Integral elastic, electronic-state, ionization, and total cross sections for electron scattering with furfural

“…7 In electron collisions with polar molecules or for dipoleallowed singlet transitions, we employ a Born-closure scheme to deal with the long range potential. 43 The scattering amplitude within the Born-closure is given by…”

Excitation of vibrational quanta in furfural by intermediate-energy electrons

“…An additional error due to our analyser transmission calibration (∼20%) must also be considered. While the inherent error in our SMCPP elastic DCS computations is negligible, we have found from past experience 28,48 that it can often reproduce the experimental data to 10% or better between 20 and 40 eV. Hence, a 10% uncertainty on our elastic DCS has been incorporated into our analysis.…”

“…(1) that the product R i × σ 0 gives the required composite vibrational mode DCSs provided the elastic DCSs (σ 0 ) are known. Those results, for bands I and II, can also be found in Tables II and III. In this study, we have utilised the parallel version of our Schwinger Multichannel with norm-conserving pseudopotentials (SMCPP) computation approach, 48 which incorporates single-excitation configuration interaction techniques for the target description, for the elastic DCSs at 20 eV, 30 eV, and 40 eV. Note that no measured elastic DCSs for electron scattering from furfural are currently published, and given the challenges we found in using furfural, we are sceptical that any applications of the relative flow technique 49 to attempt such measurements are likely.…”