The metastable Cs-Ci center was studied by means of infra-red absorption spectroscopy. Following the electron irradiation of C-doped material, new infra-red absorption lines at 540.4, 543.3, 579.8, 640.6, 730.4 and 842.4/cm were observed. The lines were identified as being local vibrational modes of the Cs-Ci center in its B-form. Illumination of the sample with band-gap light at about 60K converted the B-form to the A-form, and local modes of the A form were identified at 594.6, 596.9, 722.4, 872.6 and 953/cm.

Local Vibrational Modes of the Metastable Dicarbon Center (Cs-Ci) in Silicon E.V.Lavrov, L.Hoffmann, B.Bech Nielsen: Physical Review B, 1999, 60[11], 8081-6