We have applied laser-induced breakdown spectroscopy to quantitative analysis of colloidal and particulate iron in water. A coaxial sample flow apparatus developed in our previous work, which allowed us to control the atmosphere of laser-induced plasma, was used. Using sequential laser pulses from two Q-switched Nd:YAG lasers as excitation sources, the FeO(OH) concentration in the tens of ppb range was determined with an optimum interval between two laser pulses and an optimum delay time of a detector gate from the second pulse. The detection limit of Fe decreased substantially using two sequential laser pulse excitations:  the 0.6 ppm limit of single pulse excitation to 16 ppb with sequential pulse excitation. The effects of the second laser pulse on the plasma emission were studied. The concentration of iron in fine particles in boiler water sampled from a commercially operated thermal power plant has been determined successfully by this method. The results show the capability of laser-induced breakdown spectroscopy in determining suspended colloidal and particulate impurities in a simple and quick way.

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The reactive pyrolysis-gas chromatography technique was applied to verify the branching and/or cross-linking structures in an industrially available PC sample and its thermally treated ones through identification of specific pyrolysis products directly reflecting the related abnormal structures. On the pyrograms of the thermally treated samples, the peaks reflecting the abnormal structures such as branching and/or cross-linking were observed together with those reflecting main chain and end groups. Although the formations of these branching and/or cross-linking structures during the thermal treatment of PC had been suggested early, the identification of these pyrolysis compounds by reactive pyrolysis verified the existence of these structures. Furthermore, the fact that some of those characteristic peaks were also observed on the pyrogram of the industrially available PC sample prepared by the melt method indicated that the branching and/or cross-linking reactions would occur to some extent in the industrial polymerization reactor to synthesize the PC by the melt method.

Photodissociation processes of the doubly excited states of H2 into H(2p)+H(2p) have been studied using a coincidence detection of two Lyman-α photons. Coincidence spectra have been measured in the energy region of 29.0–36.0 eV. The intensity of the observed coincidence peak corresponding to two Lyman-α photons increases with increasing energy from its threshold which is about 29 eV. The main precursor of the two H(2p) atoms is assigned to the doubly excited Q2 1Πu state.

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Laser-induced cavitation has mostly been studied in bulk liquid or at a two-dimensional wall, although target shapes for the particle synthesis may strongly affect bubble dynamics and interfere with particle productivity. We investigated the dynamics of the cavitation bubble induced by pulsed-laser ablation in liquid for different target geometries with high-speed laser microsecond videography and focus on the collapse behaviour. This method enables us observations in a high time resolution (intervals of 1 μs) and single-pulse experiments. Further, we analyzed the nanoparticle productivity, the sizes of the synthesized nanoparticles and the evolution of the bubble volume for each different target shape and geometry. For the ablation of metal (Ag, Cu, Ni) wire tips a springboard-like behaviour after the first collapse is observed which can be correlated with vertical projectile motion. Its turbulent friction in the liquid causes a very efficient transport and movement of the bubble and ablated material into the bulk liquid and prevents particle redeposition. This effect is influenced by the degree of freedom of the wire as well as the material properties and dimensions, especially the Young's modulus. The most efficient and largest bubble movement away from the wire was observed for a thin (500 μm) silver wire with velocities up to 19.8 m s(-1) and for materials with a small Young's modulus and flexural rigidity. We suggest that these observations may contribute to upscaling strategies and increase of particle yield towards large synthesis of colloids based on targets that may continuously be fed.

Stress enhancement in laser-induced shock process by plasma-confining effect of liquid overlay was demonstrated visually and its dependence on liquid layer thickness was studied. Time-resolved photoelasticity imaging technique in bright-field mode was used to observe the stress wave in solid phase and the shock wave, plasma, and cavitation bubble in the liquid phase simultaneously. From the photoelastic images, intensity of the laser-induced stress wave (LSW) inside a solid was evaluated semi-quantitatively. We prove that LSW is weaker with thinner liquid layer. To achieve the same effect with bulk liquid, the liquid film needs to be thicker than a threshold value.

Absolute measurements of the photoionization and photodissociation cross sections of C H h b d · .2 2 ave een rna e usmg contmuum monochromatized synchrotron radiation in the 53-93 nm region. The absolute photoabsorption cross section and photoionization quantum yield of C 2 H 2 have also been measured. The excitation spectra ofC, and H(Lyman-a) fluorescence have also been obtained. The obtained results have been compared with theoretical calculations. An unresolved problem of the spectral. interpretation concentrated on the (J * and 1T* shape resonances has been clarified by the ~tr~l~htforward demonstration of the photoionization quantum yield. The ionizing and nomomzmg decay processes of the superexcited C Z H 2 molecules have been discussed in view of the strong competition of autoionization and neutral dissociation. An overlapping nature of Rydberg states with the shape resonance is found to be important. 4142