Structural changes in electron-irradiated paraffin crystals at < 15K and their relevance to lattice imaging experiments

Abstract

The process of electron beam irradiation of orthorhombic monolamellar microcrystals of the n-paraffin n-tetratetracontane cooled < 15K is monitored by changes in the crystal structure to give a much clearer view of the beam damage process than is afforded by plots of diffraction intensity variation. The observed structural change in the chains, observed in the projection down the chain axes as an increasingly circular cross-section, is consistent with previous structural analyses of structural damage in an orthogonal view and also other observations of conformational flexibility of long chains induced by trans-vinylene groups. Nevertheless, within the 2.5 Å resolution available for direct lattice images (reported elsewhere), there is virtually no detectable structural change at the 10 e A -2 electron dose used for these exposures.