Colour centres in potassium chlorate, KClO<inf>3</inf>

The absorption spectrum of a X-ray irradiated KClO3 crystal is reinvestigated and the results are discussed in relation to the earlier work. A new band with a sharp peak at 218 mμ is reported and attributed to be due to perturbation of the fundamental absorption of the crystal by the presence of point defects. The spectrum of the solution of the coloured crystal has been fully accounted for by assuming the presence of ClO2, ClO2- and ClO-. The effects of optical bleaching on the absorption spectra are reported. The band in the visible region (450 mμ) is shown to have a gaussian shape with 0·56 eV half width. This band is attributed to O3- trapped in the crystal probably at a negative ion site after some rearrangement of oxygens formed as products of radiolysis. From the g-value of approximately 2·01 and negligible g-anisotropy of the strong central band of the e.s.r. spectrum and its relative thermal stability, the view is advanced that it is probably due to O3- rather than to O2- as suggested by Hasty. This assignment is in conformity with what was reported earlier in the case of coloured NaClO3·. © 1968.