It was recalled that the nature of the GR2-8 absorption lines had not been fully established. These were very sharp lines which reflected transitions from the ground state of the neutral vacancy to at least 13 nearly degenerate excited states with 3-fold degeneracy. Recent experiments had provided information on 3 charge states of the vacancy. These data were analyzed here by using a model which permitted the energies of states which had not yet been observed to be predicted. It was proposed that there was another vacancy 1-electron state, not composed of dangling bond states, which were located near to the valence band. The GR2-8 transition was attributed to a 2-electron transition.

A.Mainwood, A.M.Stoneham: Materials Science Forum, 1997, 239-241, 99-102