Quartz spectral transmission

Figure 21. Spectral transmission of a 100-nm layer of hydrogenated amorphous Si deposited by plasma CVD of a silanethelium mixture on a Suprasil quartz substrate. (Reproduced with permission from Ref. 53.)...

A further development of mixing and reaction is ultraviolet (UV) digestion. Flere a quartz coil is wrapped around a UV lamp so that the sample stream is irradiated. Depending on the type of lamp and the spectral transmission characteristics of the coil, this can cause total breakdown of complex compounds, such as in the degradation of organic molecules in the presence of an oxidant for the subsequent measurement of total N, C, or, with milder conditions, partial decomposition as in the breakdown of complex cyanides to FICN. 

For prism spectrometers, the spectral transmission depends on the material of the prism and the lenses. Using fused quartz, the accessible spectral range spans from about 180 to 3000 nm. Below 180nm (vacuum-ultraviolet region), the whole spectrograph must be evacuated, and lithium fluoride or calcium fluoride must be used for the prism and the lenses, although most VUV spectrometers are equipped with reflection gratings and mirrors. 

Nonetheless, near-IR is the most widely used IR technique. Less intense water absorptions permit to increase the sampling volume to compensate, to some extent, for the lower near-IR absorption coefficients and the inferior specificity of the absorption bands can for many applications be overcome by application of advanced chemometric methods. Miniaturised light sources, various sensor probes, in particular based on transmission or transflectance layouts, and detectors for this spectral range are available at competitive prices, as are (telecommunications) glass or quartz fibres. 

Figure 3.3 Relative spectral energy distribution of a 125W medium pressure Helios Italquartz Hg lamp and transmission curves of glass cut off filters quartz ( ), Vycor ( ),...

Figure 1. Spectral dependencies of transmission coefficients for a monolayer of surface oxidized Cu nanogranules with the diameter of 8 nm deposited on the quartz substrate. Curves 1, 2 correspond to the measured values of direct (Tdi,) and diffuse (Tjif) transmission, respectively. Curves 3, 4, 5 depict calculated coherent transmission for a monolayer of homogeneous Cu spherical nanoparticles (3) and monolayers of two-layered particles with a Cu core covered with CU2O (4) or CuO (5) shell (shell thickness is 1 nm) surrounded by Si02 (20 nm), Relative surface concentration of particles is 0.72.

Figure 2. Calculated spectral dependence of coherent transmission coefficients for a monolayer of Cu nanogranules on a quartz substrate with regard to chains (individual granule diameter is 5.4 nm).

The observation window of experimental section is as shown in Figure 5. Transmission diameter of circular window is 300 mm K9 glass and quartz glass (SI) are used in flow optical display and spectral measurement respectively. Considering optical... 

Thin films of (2,5-DM-DCNQI)2M (M=Cu, Ag) were prepared by the vacuum deposition and thermal treatment technique employed previously for analogous TCNQ-based materials (16,17). Thus, succesive layers of acceptor and metal were vacuum-deposited on the appropriate substrate to achieve a 2 1 DCNQI rmetal molar ratio. The so-obtained thin films were heat-treated at ca 150 C for a few minutes, to result in light-blue films for M=Ag and goldish films for M=Cu. Various substrates, such as quartz, KBr or CaF2 were used for transmission spectroscopic measurements covering the mid-infrared to uv spectral range. 

The NIR transmission measurements were made in the region of 12,000-4000 em by using a Bruker Vector 22/N FT-NIR spectrometer equipped with a Ge diode detector. A total of 32 scans were collected on each sample with a spectral resolution of 4 cm . The quartz cell was thermostatted at 25°C during the measurements. A total of 120 NIR spectra were acquired for each adulterant. 

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