Csl substrates

The most widely used fiat detector (FD) design is based on a two-level, indirect conversion process of X-rays to light (Granfors et al. 2001 Antonuk et al. 1997 Spahn et al. 2000 Yamazaki et al. 2004 Ducourant et al. 2003). In the first step, the X-ray quantum is absorbed by a fluorescence scintillator screen, e.g., a cesium iodide (Csl) substrate, converting it into visible light. In the second step, this light is received by a photodiode array, e.g., based on amorphous silicon (a-Si), and converted into electrical charge. 

The efficiency of many mid-infrared beamsplitters is usually worse between 600 and 400 cm than at higher wavenumbers unless a Csl substrate has been specified. 

In the event that a spectroscopist is keenly interested in the region below 600cm we strongly recommend that 100% lines be measured in the region between 600 and 400 cm before deciding which instrument to purchase. If the performance of a spectrometer equipped with a KBr beamsplitter is inadequate, a beamsplitter with a Csl substrate should be used. 

In the absence of S2, the true Michaelis constant, Kml, is obtained. Consequently, the values of f and Vmax determined in a kinetics study depend upon the composition (csl and cS2) and total substrate concentration within the system. 

In comparison, the measurements of Lukirskii (48) and lyesaar (49) are of the QDE of evaporated Csl coatings on flat substrates, and not on MCP s. These show the QDE peak associated with the strong absorption (4d - 4f transition) peak of Csl at about 100 eV. This agrees with the results obtained by measurement of the photoemission current from Csl evaporated coatings (50, 51). The high yields obtained on flat substrates will be reduced proportionally by the open area of the MCP unless a deflection grid is used. 

Some work has also been done with Csl transmission photocathodes (53, 54). Bateman (54) has used low density (5% relative density) Csl layers on thin aluminum substrates and has obtained high efficiencies (60%) in the X-ray region (6 - 20 keV). For work at longer wavelengths, very thin foil substrates are required. Another method has been used by Carruthers (53), where the Csl photocathode is deposited on a fine mesh grid (36% open area), which is placed in front of the MCP. Due to the reduction in sensitive area, however, the efficiency obtained was somewhat less than that for opaque photocathodes. 

The 1 1 photocathode projection scheme uses UV radiation to irradiate a Csl photocathode, which is masked hy a thin metal pattern. Photoelectrons are ejected from the cathode and accelerated to the wafer, which acts as the anode. A uniform magnetic field is used to focus the electrons at the wafer. Chromatic aberrations tend to limit resolution in these systems. Other problems that have been identified to hamper this technique include issues such as the uniformity of the electric and magnetic fields, substrate flatness requirements, and poor cathode life. ... 

FIGURE 51.2 Fabrication of microchannels in a polymer substrate using E CSLs and solvent bonding (additional details are in the text). 

The four machines represented four distinct technologies. The GE machine, the commercial version of the prototype used in the Colorado-Massachusetts trial, used an 18 x 23 cm area ( flatpanel ) detector consisting of a cesium-iodide (Csl) phosphor bonded to an amorphous silicon substrate containing a rectangular photodiode array. The Csl phosphor converts the incident x-rays to light, which are then detected by the photodiode array. A thin-film transistor array deep to the amorphous silicon layer processes and transmits the electronic signal to the external electronics. The pitch (size) of a detector element in this system was 100 pm. 

Kurtikyan, Ford, and coworkers have used infrared and UV spectroscopy to probe the species formed in the interaction of NO, molecules with micro-porous solvent-free layers of (por)M complexes (M=Mn (138—140), Fe (141—150), Co (151-155)) at varying temperatures. Sample preparation of such (por)M layers and their interactions with NO, have been described in detail elsewhere (156,157). Importantly, in this sample preparation technique, the (por)M species are sublimed onto KBr, Csl, or Cap2 substrates at low temperature to form porphyrin sponges which permit diffusion of volatile Hgands into the bulk layer (158). Using this method, clean IR spectra... 

Figure 2.1 Possible matrix setups (only the cryostat head carrying the matrix substrate is shown), (a) Measurements in transmission through a Csl window, (b) Measurements in reflectance from a Cu block (ideally coated with a thin Rh layer).

FIGURE 2.42 Coulometric experiments on deposited amounts of Pd on a gold substrate. Variation of Q (stocked amounts of charge at -2.3 V) upon deposited amounts of Pd (by means of galvanostatic deposits from PdClj). Solution 0.1 mol.L" Csl in DMF. (Cougnon, C., Ph.D. thesis, Universite de Rennes 1, 2002.)... 

The CsI-f-TMAE photocathode ha,s been chosen for its speed, high efficiency and simplicity. A Csl reflective photocathode, vacuum deposited on a metal substrate, adsorbs a thin layer of TMAE when a low concentration of TMAE gas flows over the surface for about one hour [12]. Such a sensitized photocathode has an extremely high quantum efficiency (46% at 175 nm). 

A variant of the above method that we developed in our laboratories in the 1980s [7] consists in co-depositingthe substrate with a large excess of Ar on a Csl crystal held at about 20 K, where the Ar solidifies instantly and encloses the substrate molecules largely within individual cavities (matrix isolation). Ar is chosen because it is transparent from the far UV to the far IR (which makes it possible to record vibrational spectra) and has in addition a very high cross section... 

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