![]() Sometimes it has been called ultraresolution, or hyperresolution. We do not regard this as superresolution. A pupil filter does not affect the spatial frequency cut-off, and therefore the Abbe resolution is unchanged, although the resolution given by the generalized Rayleigh criterion may be improved. However, this is often accompanied by a restriction in the field of view, due to appearance of giant side-lobes. Toraldo di Francia has shown that the central lobe of the point spread function can be made arbitrarily small by modifying the weighting of the pupil, a phenomenon known recently as superoscillations. ![]() The fact that Abbe and Rayleigh both seemed to consider the image of a single point as an unsatisfactory resolution criterion is worth noting. The diffraction image of a single point object was calculated by Airy back in 1835, well before Abbe’s theory. Many papers claim resolution figures based on measurement of the size of an image feature, such as a point object. Sheppard, in Comprehensive Nanoscience and Nanotechnology (Second Edition), 2019 4.01.2 Sharpening the Point Spread Function Lithium carbonate is the most important industrial compound of lithium and is the starting point for the production of most other lithium compounds.Īlberto Diaspro. The chapter also discusses the methods of production of alkali metals. One of the most remarkable features of the alkali metals is their ready solubility in liquid ammonia to give bright blue, metastable solutions with unusual properties. All the alkali metals have characteristic flame colorations because of the ready excitation of the outermost electron, and this is the basis of their analytical determination by flame photometry or atomic absorption spectroscopy. The chapter illustrates the atomic, general, physical, and chemical properties of alkali metals. Lithium is harder than sodium but softer than lead. All elements are silvery-white except cesium, which is golden yellow in color. The group 1 elements are soft, low-melting metals that crystallize with bcc lattices. This chapter discusses the discovery, isolation, abundance, and distribution of the alkali metals-lithium, sodium, potassium, rubidium, cesium, and francium. In Chemistry of the Elements (Second Edition), 1997 Publisher Summary
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