Radiolysis of strontium fluoride

Undoped alkaline earth fluorides are strongly resistant to coloration at room temperature by X-rays. However, the crystals colour fairly readily at 77 K and lower temperatures. The present paper shows that the colourability of SrF 2 at 4 K is comparable with that of K Br. However, the colourability falls sharply by a factor of about 5 at 34 K and a further fall occurs at 67 K. X irradiation of SrF 2 at 77 K and lower temperatures produces F centres and V K centres; the number of H centres formed is always more than two orders of magnitude smaller than that of V K centres. The F band shows partly resolved structure and this is more extended for irradiation below 34 K than above.