OD approach to the polytypism in CdP2

The structures of CdP₂ are described as stacking sequences of layers of CdP₄ tetrahedra. On the basis of the OD theory of Dornberger-Schiff, the stacking possibilities are derived and convenient stacking notations proposed. The idealized layer structure is given, the percentage of α-CdP₂ for any stacking sequence defined. The symbol of the OD groupoid family is P11(n)2m · (4) x, y with parameters x = y = 1/2 and (4⁺), (4⁻) as the two alternative transformations from layer to layer. The net constants are a = b ≈ 5.29 Å; the “thickness” of a layer is c₀ ≈ 4.95 Å.     

Study on particle removal efficiency of an impinging jet by an image-processing method

 An image-processing method is proposed to obtain the distribution of the removal efficiency of particles on a plate by an air jet. This method can be used to measure particle removal from a flat surface by processing the image of the reflected light from the surface. Factors affecting the particle removal efficiency such as air pressure, distance between the nozzle and the impinging surface and the impinging angle are discussed. Optimal conditions are determined to obtain the most effective particle removal by the air jet. Received: 10 April 2001 / Accepted: 2 August 2001     

Determination of delta13 CV-PDB and delta15NAIR values of cocaine from a big seizure in Germany by stable isotope ratio mass spectrometry

In this study, delta(13)C(V- PDB) and delta(15)N(AIR) values of 132 cocaine samples from a big seizure in Germany in 2002 were determined using elemental analyser isotope ratio mass spectrometry. The 1.2 tons of cocaine were packed in 1 kg packages and the cocaine bricks inside these packages showed certain logos. Twenty different logos could be identified. Results show a large variability among some samples, for delta(15)N(AIR) values ranging from-17 to -2 per thousand. Furthermore, the possibility of linking samples with the same logo was checked. The results show that, in general, there is no relationship between the determined isotope ratio and a certain logo.     

Raman and inelastic neutron scattering study on a melt-infiltrated composite of NaAlH4 and nanoporous carbon

Inelastic neutron scattering and Raman scattering spectra of a melt-infiltrated composite of NaAlH(4) and active carbon fibers have been measured at low temperature for two sample conditions: as prepared and subjected to hydrogen desorption-absorption cycling. After a careful data analysis, the present experimental results have been compared to the corresponding spectroscopic data taken from bulk NaAlH(4) and Na(3)AlH(6). Evident signatures induced by infiltration process onto the NaAlH(4) phonon bands have been detected, showing up as a strong peak broadening and smoothing together with, in some cases, an energy shift. Traces of Na(3)AlH(6), appearing as an extra intensity between 130 and 200 meV, seem also confirmed. A substantial agreement between neutron and Raman measurements has been found for the as-prepared melt-infiltrated sample, while for the cycled sample the two techniques produced rather dissimilar results. However, this apparent discrepancy can be explained by considering the different penetration depths of the two spectroscopic probes. Further work, both experimental and based on ab initio simulations, is surely needed in order to rationalize the finding of the present measurements.     

Analysis of ionic solids with SNMS

Summary The application of plasma-based SNMS to salt samples was examined to reveal the analytical features of this technique for the analysis of environmental material, which is frequently composed of ionic compounds. 10¹⁶ s^–1 cm^–2 argon ions of 300–500 eV energy were used to sputter halides, sulfates, nitrates and carbonates. The mass spectra are dominated by atomic signals of all elements of the salt and contain additional minor signals of binary homo- and heteroelemental clusters. The latter, such as salt monomers of alkali halides, are useful for compound identification. In sputter equilibrium the atomic mass signals can be used for elemental quantitation with a matrix dependence of about ±30% for the detection factors of most elements. As the average elemental detection factors are shown to be governed by atomic ionization probabilities the erosion flux from salts comprises mainly atoms. Results indicate that thermal release of atoms as well as emission of clusters are the main cause of the matrix dependence. The relative yield of the clusters was found to be strongly enhanced with increasing mass difference of the combined ions. The sputter yield of NaCl was determined to be 3.3 atoms/projectile at 490 eV argon ion energy which results in a depth propagation of 5 nm/s for the given sputter conditions.     

Crystal structure of the cyclotetraphosphate Ca2[P4O12] · 4 H2O

Ca₂[P₄O₁₂] · 4 H₂O crystallizes in the monoclinic space group P2₁/n, a = 7.668, b = 12.895, c = 7.144 Å, β 107.00°, D_x = 2.28 g · cm^?3, Z = 2. In the structure there are ringlike anions, which are composed of 4 PO₄ tetrahedra connected by oxygen bridges. The Ca²⁺ are surrounded by 7 oxygen atoms. Each two cation polyhedra are connected by a common edge to pairs which are isolated from one another. The water molecules form hydrogen bridges with one another and with the anion rings.