Study of exchange in collisions of polarized electrons with atoms and molecules

Abstract

Exchange collisions of electrons with Na and Hg atoms and O2 and NO molecules have been studied by means of polarized electrons for energies between 4 and 15 eV and scattering angles ranging from 0° to 110°. While significant exchange effects have been observed for collisions of electrons with Na and Hg atoms, in agreement with theoretical predictions, differential spin-exchange cross sections for elastic collisions from the open-shell molecules O2 and NO are much smaller. This was not anticipated before. A satisfactory explanation of this different behavior is still missing.

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

“…A very interesting feature of electron collisions against an open-shell target, is that it allows the spin flip of the scattering electron even at zero impact energy. Hegeman et al [118] have shown that in atomic target gases (Na and Hg), the spin flip differential cross sections vary strongly with respect to scattering angle while for molecules like O 2 and NO they were relatively smooth. In our first application [119] of the SMC method for electron scattering from the open-shell O 2 , we confirmed the experimental data and showed a strong dependence of the DCS with respect molecular orientation and that the interference pattern (so common in atomic cases) was washed out by the molecular orientational averaging.…”

Spin exchange in elastice-O2collisions

“…At this energy the region around 50' shows strong depolarization while elsewhere the polarization ratio is close to unity. On the other hand, at 4 eV depolarization occurs over a wide angular region [7] [7]. This strong dependence of the differential cross sections with respect to the orientation of the molecule may be useful in studies of adsorbate orientation using polarized electron beams on molecules adsorbed on surfaces.…”

“…With these considerations, the significant depolarization seen around 50' at 12.1 eV for elastic collisions with Na atoms [7] should probably be attributed to interference. At this energy the region around 50' shows strong depolarization while elsewhere the polarization ratio is close to unity.…”

Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence

“…The Münster group of Hanne studied the differential scattering of 10 eV electrons with polarization P by Na, Hg, O 2 , and NO [9,10]. (Mercury has a singlet ground state, Na and NO have open-shell doublet ground states, and the ground state of O 2 is a triplet.)…”