CARBON ... AND ITS ANALYSIS

There are many allotropes of carbon each with special properties, but the form that is the most dramatic is unquestionably diamond with its suite of physical properties that in so many instances represent extre mes. Early (including nuclear) analytical studies revealed that even t he purest of gem quality diamonds of natural origin hosts a wide range of defects, both of structural nature and in the form of inclusions o f foreign materials. Much of diamond physics is concerned with the ide ntification of the nature of these defects. Most analytical techniques are sensitive to a defect in its relationship to its immediate molecu lar environment - herein lies an advantage of nuclear analytical metho ds, since they analyse for the total elemental composition and not jus t that part associated with, for example, a particular chemical form. We consider in this paper the vast array of nuclear analytical evidenc e now assembled in relation to diamond: from instrumental neutron acti vation analysis, simple ion beam analysis, time dependent perturbed an gular distribution studies, muons and muonium, positron annihilation, in-beam Moessbauer and beta-NMR. We draw attention to the differences revealed as between natural and synthetic (high pressure high temperat ure synthesis and chemical vapour deposition synthesis) diamonds. We a ddress specifically the nature of the bonding of hydrogen in diamond, as this represents the most simple of all dopants. Some consideration is given to recent measurements on the lattice location of boron and o f iron in diamond. (C) 1998 Elsevier Science B.V.