Use of zone correction plates and other techniques for structure determination of aperiodic objects at atomic resolution using a conventional electron microscope

Abstract

Electron microscopy using microscopes with conventional magnetic lenses is restricted in resolution by spherical aberration. The ‘zonal correction principle’ allows this limit to be overcome. Its use in image reconstruction schemes allows separation of the influence of defocusing, astigmatism, etc., from the physically significant structure. The use of three-dimensional methods of image differencing is necessary in order to get interpretable results in the study of the not ‘infinitely thin’ objects in electron microscopy at atomic level. The use of redundancy principles (similar to X -ray structure determination) is discussed and demonstrated. The most severe difficulty, especially in electron microscopy of organic specimens, is radiation damage.