Satellite-zero method

Figure 2-27. Evaluation of satellite peaks. SZ satellite-zero methods S satellite method.

The spurious or satellite term in the solution is introduced by using a second-order difference equation to approximate a first-order differential equation. An extra condition is needed to fix the solution of the second-order equation, and this condition must be that the coefficient of the spurious part of the solution is zero. In the general case of a nonlinear difference equation, no method is available for meeting this condition exactly. 

The information obtained from the phosphorescence microwave double resonance (PMDR) spectroscopy nicely complements the results deduced from time-resolved emission spectroscopy. (See Sect. 3.1.4 and compare Ref. [58] to [61 ].) Both methods reveal a triplet substate selectivity with respect to the vibrational satellites observed in the emission spectrum. Interestingly, this property of an individual vibronic coupling behavior of the different triplet substates survives, even when the zero-field splitting increases due to a greater spin-orbit coupling by more than a factor of fifty, as found for Pt(2-thpy)2. 

By monitoring excitation spectra with a time-resolved detection of the emission, briefly called time-resolved excitation spectroscopy , it is possible, to identify specific relaxation paths. Although, these occur on a ps time scale, only measurements with a ps time resolution are required. It is shown that the relaxation from an excited vibrational state of an individual triplet sublevel takes place by a fast process of intra-system relaxation (on the order of 1 ps) within the same potential surface to its zero-point vibrational level. Only subsequently, a relatively slow crossing to a different sublevel is possible. This latter process is determined by the slow spin-lattice relaxation. A crossing at the energy of an excited vibrational/phonon level from this potential hypersurface to the one of a different substate does not occur (Fig. 24, Ref. [60]). This method of time-resolved excitation spectroscopy, applied for the first time to transition metal complexes, can also be utilized to resolve spectrally overlapping excited state vibrational satellites and to assign these to their triplet substates. 

First, the authors stated that the reduced catalyst surface contained only zero-valent iron. This is based on the analysis of the raw data from the Fe 2p 3/2 spectra. It has been found, however, that it is impossible to identify small levels of oxidized iron in the presence of a large fraction of metallic iron. This is due to the wide distribution of intensity for iron compounds caused by their satellite structure. It is therefore believed that the catalyst described in Ref. 19 contained a similar fraction of iron oxide to the present samples activated with the dry method (see Fig. 2.40). This is in line with the expectation that the presence of the spinel-forming aluminum oxide prevents complete reduction. It should be pointed out that Mossbauer spectroscopy, thermogravimetric reduction, and energy dispersive X-ray analysis all showed a small fraction of oxidized iron to be present within the bulk of fully reduced samples. 

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