Photoconductivity in irradiated diamond

Measurements are reported of the photoconduction spectra of several electron irradiated type Ia and type IIa diamonds in the neighbourhood of the GR1 and ND1 absorption systems, and the absorption lines which have been labelled GR2 to GR8, R9 and R10. Minima occur in the photoconduction spectra at the positions of maxima in the GR1 absorption system. Sharp peaks which persist at temperatures down to 8 K are observed in the photoconduction spectra at the positions of maxima in the ND1 absorption system and the lines GR2 etc. Mechanisms which might give rise to these sharp photoconduction peaks are discussed.