Observation of the H2 defect in gem-quality type Ia diamond

Abstract

Abstract The H2 defect with its zero-phonon line at 986.1 nm (1.257 eV, 10141 cm −1 ) was first described in 1956 and characterized in detail in 1990–91. In this paper, the observation of strong H2 bands in greenish-yellow natural type Ia gem-quality diamonds is reported. These ‘H2 diamonds’ were apparently subjected to a treatment possibly involving irradiation and clearly involving high temperature annealing. Besides burns on the surface and in fractures, they typically showed strong green luminescence associated with brownish-yellow graining, strong H3/H4 bands, weak to strong H2 bands, and no H1b/H1c lines. Some stones displayed a weak 637 nm line as well. A model explaining the formation of the H2 defect in type Ia diamond is proposed based on the stability and interaction of defects in diamond as a function of temperature and time.