Transmittance of cultured crystalline quartz in the vacuum ultraviolet before and after electron irradiation.

The transmittance of cultured crystalline quartz has been measured in the vacuum uv from 2000 A to its cutoff wavelength. For most samples this cutoff wavelength is approximately 1450 A, but some samples had very low transmittances to wavelengths as long as 1600 A. Furthermore, in the spectral region from 1450 A to 2000 A, all the samples had nonuniform transmittances as a function of position on the sample. Most of these nonuniformities are quite pronounced close to the cutoff wavelength but disappear or are very small at 2000 A. After irradiation with 1-MeV electrons, the transmittances of the good, fairly uniform, samples were practically unchanged. However, areas of some of the less uniform samples became quite black to the eye and practically nontransmitting in the vacuum uv. In most cases, blackened and nonblackened areas, on the same sample, had quite sharp boundaries, on the order of 1 mm or less. The blackened areas had excess aluminum and alkali impurities as determined by paramagnetic electron resonance measurements. A short comparison is made between cultured crystalline quartz and various types of fused silica.