Laser rapid-flow method

Method. The laser vaporization source eliminates the material constraints inherent in conventional oven sources. This is accomplished by localizing the heating to a very small area at the surface of the sample and by entraining the vapor produced in a rapid flow of high pressure gas. 

It is noticeable that the shortenings of the Pt-Pt and Pt-P distances, A(Pt-Pt) and A(Pt-P), of the Pn and Bzte crystals are 0.0081(3) and 0.005(1)A, and 0.0127(5) and 0.008(1) A, respectively, which are the largest two among the five crystals. The ratios of A(Pt-Pt) / A(Pt-P) are 1.62 and 1.59 for the Pn and Bzte crystals, respectively, which are very close to each other. This suggests that the excited diplatinum complex anion may have the same structure in the two crystals, and the concentrations of the excited molecules may be different between the two crystals. On the other hand, the excited structures in the Bu, Bztbu and Bzdmp crystals may be different due to the different crystal environment. The change at the excited state is schematically drawn in Fig. 7.26. Not only the Pt-Pt distance but also Pt-P distance is shortened at the excited state of the diplatinum complex anion, which is in good agreement with the experimental results observed from the combination of the EXAFS method with rapid-flow laser spectroscopy [54]. 

Particle size is one of the principal determinants of powder behavior such as packing and consolidation, flow ability, compaction, etc., and it is therefore one of the most common and important areas of powder characterization. Typically, one refers to particle size or diameter as the largest dimension of its individual particles. Because a given powder consists of particles of many sizes, it is preferable to measure and describe the entire distribution. While many methods of size determination exist, no one method is perfect (5) two very common methods are sieve analysis and laser diffraction. Sieving is a very simple and inexpensive method, but it provides data at relatively few points within a distribution and is often very operator dependent. Laser diffraction is a very rapid technique and provides a detailed description of the distribution. However, its instrumentation is relatively expensive, the analytical results are subject to the unique and proprietary algorithms of the equipment manufacturer, and they often assume particle sphericity. The particle size distribution shown in Figure 1 was obtained by laser diffraction, where the curves represent frequency and cumulative distributions. 

Kinetic experiments are performed in two different ways. In one an initial disequilibrinm exists between two or more reactants, which after being rapidly mixed, combine to react toward equilibrium see Rapid Scan, Stopped-Flow Kinetics). Ideally, the mixing time is short with respect to the timescale of the reaction or actually with respect to the formation of intermediates. In contrast, in the relaxation experiment, the reactants are together and in equilibrium, and the whole system is instantaneously displaced from equilibrium. Subsequently, the system relaxes to the same or a new equilibrium state. Table 1 suimnarizes the approximate time resolution of various commonly applied mixing and relaxation techniques. The table indicates the superiority of the relaxation methods with respect to time resolution, mainly due to the development of ultrafast lasers. Mixing liquids on the (sub)microsecond time scale appears to present an important experimental barrier. 

The highest throughput can be achieved by the combination of flow cytometry and cell sorting. This is a rapid method for the analysis of single cells as they flow in a liquid medium through the focus of a laser beam surrounded by an array of detectors. By simultaneous use of different fluorescent stains, flow cytometry can yield multiparametric data sets which are, however, often difficult to interpret [88]. These are then used to discriminate between different types of cells, a procedure that is suitable for rapid enrichment of certain types of cells from large populations. An important and potentially very useful contribution to flu-... 

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