Activation of single phonon infra-red lattice absorption in neutron irradiated diamond

The activation of a band in the absorption spectrum of a type IIa diamond was accomplished using fast neutrons. The absorption spectra taken before and after a dose of 3 x 10/sup 17//cm/sup 2/ are shown. Strong continuous absorption is evidenced following irradiation, beginning sharply at the Raman energy and extending to lower frequencies. This effect can only be explained satisfactorily as single phonon lattice absorption. It is suggested that most of the damageinduced activation arises from regions of local disorder which probably involve more than 10/sup 20/ atoms/cm/sup 3/. It is concluded that absorption activation in the one phonon region by damage strongly supports the theory that it is caused by defect induced coupling to the fundamental lattice modes. (B.O.G.)