Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion
Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion of crystal lattices in crystals with relatively large lattice parameters. After the macromolecular crystals of viruses and proteins, the structures of which have been beautifully demonstrated by WyckofT (9) using replica methods, the most likely class of compounds with smaller lattice parameters are organic molecules Fig. 1. Schematic projection of platinum phthalocyanine Fig. 2. Unit cell of platinum phthalocyanine crystal. Circles molecule normal to the phthalocyanine ring (after Robertson represent molecules, the metal atoms being situated at the and Woodward 1940). • C; O CH; O, N centre of the circle.
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