Probe-matrix system

Since many experimental studies of 7-Fe were performed for 7-Fe particles in a Cu matrix (or Cu alloy, including Cu-Al) [113], [114], it is important to probe the electronic structure of the particle-matrix systems. Embedded-cluster methods are ideally taylored to treat small particles of a metal in a host matrix, a system that would require a very large supercell in band-structure calculations. DV calculations were performed for the 14-atom Fe particle in copper shown in Fig. 21 [118]. Spin-density contour maps were obtained to assess the polarization of the Cu matrix by the coherent magnetic 7-Fe particle. Examples are given in Figs. 22 and 23 for a Fe particle in Cu and 7-Fe in Cu with two substitutional Al. If the matrix is a Cu-Al alloy, this element is known to penetrate the Fe particle [114]. 

In conventional FAB (see Section 3.2.3), the analyte is mixed with an appropriate matrix material and applied to the end of a probe where it is bombarded with a fast-atom, or latterly, a fast-ion, beam. There are two major considerations when linking HPLC to such a system, namely (a) how is the matrix material, which is crucial for effective ionization in conventional FAB, to be incorporated into the system, and (b) how is the flowing HPLC system to be continuously presented to the ionizing beam ... 

When investigating opaque or transparent samples, where the laser light can penetrate the surface and be scattered into deeper regions, Raman light from these deeper zones also contributes to the collected signal and is of particular relevance with non-homogeneous samples, e.g., multilayer systems or blends. The above equation is only valid, if the beam is focused on the sample surface. Different considerations apply to confocal Raman spectroscopy, which is a very useful technique to probe (depth profile) samples below their surface. This nondestructive method is appropriate for studies on thin layers, inclusions and impurities buried within a matrix, and will be discussed below. 

CHD Re (CO) j. are very close to the gas phase positions and the shift (Mn to Re) is almost identical in gas phase and matrix. Thus, V(C-H). in the matrix will provide information on the C-H bond length. On generation of the unstable 1 2 complexes, there is a downward shift in V(C-H). of 11-14 cm implying a bond lengthening of. 0011-.00 X. This is clearly a very sensitive probe of the effect of slight electronic perturbation of the metal centre and is likely to be useful for other systems. 

In addition to structural information, Li MAS NMR Tz relaxation measurements and analysis of Li line shapes have been used to probe the dynamics of the lithium ions. Holland et al. identified two different species with different mobilities (interfacial Li (longer Tz, rapid dynamics) and intercalated lithium (shorter Tz, slower dynamics)) in the elec-trochemically lithiated V2O5 xerogel matrix. Li hopping frequencies were extracted from an analysis of the Li line widths and the appearance of a quadru-polar splitting as the temperature decreased in a related system. ... 

---