Eliminating Spherical Aberration and preserving Phase Contrast Information in Electron Microscopy

Abstract

THE method proposed here enables, in principle, the optical system of a conventional electron microscope to be used to determine both amplitude and phase, free from spherical aberration, of the electron wave transmitted through a two or three dimensional crystallite of sufficiently large unit cell. The condition that the specimen must be a crystallite is probably unavoidable in any method of high-resolution electron microscopy, because the severe electron radiation damage of organic substances will probably prevent the visualization of isolated molecules at atomic resolution. The further condition, that the two shortest unit cell dimensions of the crystallite should be more than about 10 Å (using a good conventional electron microscope), is satisfied by most substances of biological interest.