Quartz, wavelength transmittance

Figure 12. Raman spectra of ethanol on quartz measured at various values of the angles of incidence and thus, various penetration depths. In addition the transmittance spectrum of the glass filter (OG515) is shown (causing the distortion of the spectrum to the left of the cut-off wavelength).

The transmission spectra of several glasses are presented in Fig. 8-13 (Philips, 1993). In contrast to normal quartz material the transmittance of synthetic and highly pure Suprasil quartz (purity 99.9% Si02> extends down to X of about 165 nm. At 190 nm, it still has a transmittance T of over 80%, whereas the transmittance of normal quartz at this wavelength is insufficient for applications below X of 200 nm. Therefore, Suprasil quartz is best suited for the construction of VUV lamps or VUV photoreactors (see Fig.s 4-13 to 4-15). In addition, it enhances the VUV emission of MP Hg lamps when used as the envelope material (see Fig. 4-3). However, Suprasil quartz is expensive and very sensitive to mechanical strain. 

With quartz fibers it is easier to lead the optical emission into the spectral apparatus, however, it should be mentioned that the transmittance decreases seriously below 220 nm. This may give rise to detector noise limitations for analytical lines at lower wavelengths. 

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