Discernibility criterion in Fresnel projection microscopy.

The applicability of the Rayleigh separation criterion in Fresnel electron projection microscopy is studied theoretically. Quantum mechanical simulations of electron scattering by two C60 molecules, at energies of the order of 150 eV, are analysed on the basis of the discernibility criterion of two diffracting apertures. The simple separation criterion derived from Fresnel theory is found to remain pertinent, except for small source to object distances. At these distances, the critical separation distance between the two C60 molecules is such that the 'sucking-in' of the beam between the two nearby C60 molecules cannot be neglected. This leads to a discrepancy with the Rayleigh criterion.