SDDS

Fig. 4.9. Block diagram (left) and assembly image (right, also with cap removed) of a silicon drift detector (SDD) module, including electronics [4.30],...

Silicon drift detectors (SDD, Figs 4.8 and 4.9) now also provide sufficient resolution (FWHM = 0.175 keV) above a sample spot sized 2 x 2 to 100 x 100 mm, and enable high-speed operation (> 10 counts s ). SDD can be combined with microelectronics and applied in portable TXRF models for microanalytical applications [4.30]. They must be cooled by a Peltier element. 

Tab. 4.1. Certain elements whose Ka peaks interfere with escape peaks of other elements using solid state detector SSD or silicon drift detector SDD [4.16].

Table 6. B3LYP/SDD optimized structural parameters (pm, °) and dissociation (kcal/mol) of H3AI—ER( and Me3Al—ER( adducts Dg = dissociation energy at 0 energies K...

Table 7. B3LYP/SDD optimized and experimental structural parameters (in parentheses) for Et3Al—E(Tms)3 adducts (pm, °)...

Solid-state detectors based on silicon- or germanium-diodes possess better resolution than gas counters, particularly when cooled with liquid nitrogen, but they allow only very low count rates. PIN diodes have also recently become available and have been developed for the instruments used in the examination of Martian soils (Sects. 3.3 and 8.3). A very recent development is the so-called silicon-drift detector (SDD), which has very high energy resolution (up to ca. 130 eV) and large sensitive detection area (up to ca. 1 cm ). The SNR is improved by an order of magnitude compared to Si-PIN detectors. Silicon drift detectors may also be used in X-ray florescence spectroscopy, even in direct combination with Mossbauer spectroscopy (see Sects. 3.3 and 8.3). 

In addition to the Mossbauer data, SDDs allow the simultaneous acquisition of the XRF spectrum, thus providing data on the sample s elemental composition. A new control- and readout-electronics for MIMOS llA allows spectra acquisition at highest possible count rates available at a total detector area of 360 mm. ... 

Fig. 3.24 Left. Energy resolution of the silicon-drift-detectors (SDD) at 5.9 keV ( Fe radioactive source) as a function of temperature. Middle-. One segment (out of four) of SDDs composed of two individual chips with front-end electronics. The dimensions of the A1 housing are cm x 4 cm x 7 cm. In the center the opening of the radiation collimator can be seen. Right MIMOS IIA SDD segment (1/4 of the complete detector ring a 10 -cent coin is shown for comparison)...

Fig. 3.25 Left signal-to-noise ratio (SNR) of the Mbssbauer spectra of a basalt taken with MIMOS II (full SI-PIN detector system black data-points) and MIMOS IIA (1/4 of full SDD system red data-points) respectively. Right XRF spectra of low Z elements measured with MIMOS IIA (SDDs) at —20°C. The Compton scattered 14.4 keV line (at 13.8 keV) and the resonant 14.4 keV Mossbauer line are well separated...

Fig. 8.41 Left. Comparison of SNR of 14.4 keV Mossbauer spectra, taken with a Si-PIN detector system (MER instrument four diodes) and with a SDD detector system (advanced MIMOS instrument only one diode chip) Right. X-ray spectrum of a basalt (Ortenberg basalt see [366, 371], taken with a high resolution Si-drift detector system at ambient pressure (1 atm), demon-...

The miniaturized Mossbauer instruments have proven as part of the NASA Mars Exploration Rover 2003 mission that Mossbauer spectroscopy is a powerful tool for planetary exploration, including our planet Earth. For the advanced model of MIMOS II, the new detector technologies and electronic components increase sensitivity and performance significantly. In combination with the high-energy resolution of the SDD, it will be possible to perform XRF analysis in parallel to Mossbauer spectroscopy. In addition to the Fe-mineralogy, information on the sample s elemental composition will be obtained. 

Fig. 3. B3LYP/SDD optimized dissociation enthalpies De [kcal/mol] of H3AI <— ER/3 and Me3Al ER3 adducts (R7 = H, Et, /-Pr) revealing the role of the pentele center on the adduct...

As was described earlier, the internal SDD of dendrimers is remarkably high compared to traditional polymers and is well defined by a narrow transition zone at the outside. When linear polymers are forced together by increasing their concentration in a solvent, they freely interpenetrate each other due to their open structure. Dendrimers, on the other hand, appear to represent a different case, due to their compact size and architectural features. 

ECP basis sets performed as expected for these atomic systems, with the Los Alamos double-C (LANL2DZ) working best. Its MAD is only 0.82 eV. However, the 31 split-valence ECP of Stevens et al. (CEP-31G) and the Stuttgart-Dresden ECP (SDD) each generated a similar error of 0.87 eV. 

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