Positron scattering from chiral enantiomers

Abstract

We report on total cross section measurements for positron scattering from the chiral enantiomers ($+$)-methyl ($R$)-2-chloropropionate and (--)-methyl ($S$)-2-chloropropionate. The energy range of the present study was 0.1--50 eV, while the energy resolution of our incident positron beam was \ensuremath{\sim}0.25 eV (FWHM). As positrons emanating from \ensuremath{\beta} decay in radioactive nuclei have a high degree of spin polarization, which persists after moderation, we were particularly interested in probing whether the positron helicity differentiates between the measured total cross sections of the two enantiomers. No major differences were, however, observed. Finally, quantum chemical calculations, using the density functional theory based B3LYP-DGTZVP model within the gaussian 09 package, were performed as a part of this work in order to assist us in interpreting some aspects of our data.