Spontaneous Ultraviolet Emission from 233 Uranium / T 229 horium Samples

The spontaneous ultraviolet luminescence reported [G. M. Irwin and K. H. Kim, Phys. Rev. Lett. 79, 990 (1997); D. S. Richardson et al., ibid. 80, 3206 (1998)] from 233uranium compounds and ascribed to an ultraviolet gamma-ray emission from the metastable 229thorium daughter is actually N2 discharge emission induced in the air surrounding the sample by the sample radioactivity. The UV spectrum from high elemental and isotopic purity 233UO3 reported here also exhibits a line at 391.3 nm that does not appear to be due to electric discharge N2 emission.