“Carbon! … and its analysis”

Abstract

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 extremes. Early (including nuclear) analytical studies revealed that even the purest of gem quality diamonds of natural origin hosts a wide range of defects, both of structural nature and in the form of inclusions of foreign materials. Much of diamond physics is concerned with the identification of the nature of these defects. Most analytical techniques are sensitive to a defect in its relationship to its immediate molecular environment — herein lies an advantage of nuclear analytical methods, since they analyse for the total elemental composition and not just that part associated with, for example, a particular chemical form. We consider in this paper the vast array of nuclear analytical evidence now assembled in relation to diamond: from instrumental neutron activation analysis, simple ion beam analysis, time dependent perturbed angular distribution studies, muons and muonium, positron annihilation, in-beam Moessbauer and β-NMR. We draw attention to the differences revealed as between natural and synthetic (high pressure high temperature synthesis and chemical vapour deposition synthesis) diamonds. We address 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 latticle location of boron and of iron in diamond.