Da. Przybyla et al., MEASUREMENTS OF POSITRON-MOLECULE DIFFERENTIAL SCATTERING CROSS-SECTIONS, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 143(1-2), 1998, pp. 57-60
Relative differential cross-sections (DCS's) have been measured for th
e quasi-elastic scattering (elastic scattering plus rotational and vib
rational excitations) of positrons from CH4, N-2, O-2, CO, CO2, N2O, C
2H2, and SF6 molecules in a crossed-beam experiment. The energy range
extends from below the positronium (Ps) formation threshold of each mo
lecule to well above the Ps formation threshold and the angular range
extends from 30 degrees to 135 degrees. For CH4, N-2, CO, O-2, and SF6
the DCS exhibits structure (a clear minimum and maximum) at low energ
ies that tends to wash out as the energy is increased above the Ps for
mation threshold. In contrast, for N2O, CO2, and C2H2 we find no prono
unced structure below the Ps formation threshold. These comparisons su
ggest that the degree of spherical symmetry of the target may be corre
lated with the presence of the structure. (C) 1998 Elsevier Science B.
V. All rights reserved.