Molecular orbital theory of electronic transitions at the vacancy in diamond

Abstract

Abstract In diamond, a series of optical absorption lines lying between 1·66 and 3·0 eV, which have been labelled GR1 to GR8, are commonly observed. These lines are fairly sharp, and the symmetry of some of the states from which they are derived have been deduced from piezo-spectroscopic studies. Furthermore, photoconductivity indicates that the absorption lines GR2 to GR8 are associated with hole production. A model for the absorption lines is proposed and investigated. This model assumes the transitions take place around a vacancy, the vacancy being represented by a defect molecule as originally suggested by Coulson and Kearsley (1957). The lines GR2 to GR8 arise from transitions from the neutral vacancy to states associated with the negative vacancy and a hole located in one of the nearby molecular orbitals. The relative intensities of the transitions are calculated. Using results of a cluster model, the electronic orbitals occupied by the hole are located at the top of the valence band and are found t...