X band

The components of a typical EPR spectrometer operating at X-band frequencies [3, 4, 6] are shown in figure Bl.15,4. 

Figure Bl.16.2. X-band TREPR spectra obtained at 0.1 ps after 308 mn photolysis of a fliiorinated peroxide dimer in Freon 113 at room temperature. Part A is the A/E RPM spectrum obtained upon direct photolysis part B is the E/A RPM spectrum obtained upon triplet sensitization of this reaction using benzophenone.

Lau K T, Bar-Chaim N, Ury I and Yariv A 1983 Direct amplitude modulation of semiconductor GaAs lasers up to X-band frequencies Appi. Phys. Lett. 43 11... 

M. Bodenstein, Bericht des H Intemationakn Kongressesfir angewandte Chemie Berlin 1903, Sektion X, Band IV, 1904, p. 561. 

This shows that the penetration depth decreases dramatically with increasing conductivity of the medium to be penetrated. This has been plotted (Fig. 2) for different specific resistivities of the medium and the frequency of 10-40 Gc/s11 at which microwave conductivity measurements are typically performed. It can be seen that with a specific resistivity of 10 Q cm, a penetration depth of only 2 mm can be expected. Figure 2 furthermore shows the doping densities at which the respective penetration depths can be expected for silicon. Whereas the lower frequency X-band of microwaves (8-12.5 Gc/s) offers some advantages for materials with very low resistance, the high-frequency microwave Ka-band (26.5 10... 

Fig. 4. X-band EPR spectra of [Fe3S4]+ clusters in wild type and mutant forms of P. furiosus Fd. All spectra were recorded at 4.2 K microwave power, 1 mW microwave frequency, 9.60 GHz modulation amplitude, 0.63 mT. All samples were in 100 mM Tris-HCl buffer, pH 7.8.

Fig. 10. X-band and P-band perpendicular mode EPR spectra of partially reduced T. thermophilus 7Fe Fd and Fe +-EDTA. The signsd around g = 2 in T. thermophilus Fd arises from approximately 1% of S = 1/2 [FesSJ clusters in the partially reduced sample. Taken from Ref. (,94).

The aerobic and anaerobic degradation of acetone is initiated by carboxylation to acetoac-etate. The involvement of manganese has been examined in photoheterotrophically grown Rhodobacter capsulatus strain BIO and the presence of Mn verified from the X-band EPR spectrum (Boyd et al. 2004). 

ESR characterization was performed in situ in order to avoid any contact of the pretreated solids with air. Spectra, recorded as the first derivative of the absorption, were obtained at room temperature or 77K using a Varian E9 spectrometer working in the X band. The g values were measured relative to a DPPH reference (g = 2.0036). The sample tubes were filled with the solid to a height greater than the depth of the resonant cavity and the number of paramagnetic species was calculated by double integration of the recorded spectra normalized to that of Varian Strong Pitch sample (g = 2.0028, 3. lO spins, cm" ). 

The ESR measurements were made at RT or 77 K on a Varian E-9 spectrometer (X-band), equipped with an on-line computer for data analysis. Spin-Hamiltonian parameters (g and A values) were obtained from calculated spectra using the program SIM14 A [26]. The absolute concentration of the paramagnetic species was determined from the integrated area of the spectra. Values of g were determined using as reference the sharp peak at g = 2.0008 of the E i center (marked with an asterisk in Fig. 3) the center was formed by UV irradiation of the silica dewar used as sample holder. 

Figure 2.15. X-band EPR spectra recorded after NO adsorption (1 -5 torr) onto ConZSM-5, FenZSM-5 (after [64]), and Cu ZSM-5 (after [41]) zeolites.

Figure 2.20. Transformation of silica supported dinitrosyl complexes of nickel(II) leading to formation of nitrogen dioxide and its final stabilization on the support. The picture shows the molecular structure and the spin density contours calculated with BP/DNP method of the involved species, and evolution of the X-band EPR spectra of the NiN02 Si02 complex due to spillover of the ligand (adopted from [71]).

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