Positron Annihilation Lifetime Analysis of Left- and Right-Handed Alanine Single Crystals

Abstract

Studies of the interaction of polarized light or particles (including electrons, e(-), or positrons, e(+)) with asymmetric forms of matter has been of interest to scientists since the discovery of chirality and the subsequent development of particle physics. Researchers have been interested in e(+) interactions with chiral molecules for decades, but with mixed and indecisive results. After reviewing the field, we speculated that the e(+) or positronium (Ps) might interact differently with chiral pairs of large single crystals, i.e., the left-handed or right-handed asymmetric forms of the crystals - and subsequently observed significant differences in free positron annihilation and intensities in the evaluation of left-handed or right-handed quartz single crystals. This result may be understood to be a particle stereorecognition phenomenon. To extend this line of inquiry we crystallized mm scale L-or D-alanine crystals and performed positron annihilation lifetime spectroscopy measurements using a Na-22 positron source. Alanine crystals were obtained via slow evaporation of water in a Dewar, or from water/acetone solvent in a temperature-controlled environment. These methods resulted in small (approximate to 0.5 cm/side) or large (>= 1.0 cm/side) crystals, respectively. While some intensity (I-2) results from left-handed and right-handed crystals varied in positron annihilation lifetime spectroscopy analysis, the errors associated with the measurements do not indicate a stereorecognition of alanine via positron interactions.