Laser-induced chemical reaction decomposition

Rousseau and Leroi studied the two-photon-induced chemical reaction in AgCl by 30 kW ruby-laser pulses which results in a decomposition of AgCl into collodial silver and chlorine. The resultant blue-green emission was proportional to the square of the laser intensity and the measured quantum yield was 10". ... 

Conventional routes to ceramics involve precipitation from solution, drying, size reduction by milling, and fusion. The availability of well-defined mono-dispersed particles in desired sizes is an essential requirement for the formation of advanced ceramics. The relationship between the density of ceramic materials and the sizes and packing of their parent particles has been examined theoretically and modeled experimentally [810]. Colloid and surface chemical methodologies have been developed for the reproducible formation of ceramic particles [809-812]. These methodologies have included (i) controlled precipitation from homogeneous solutions (ii) phase transformation (iii) evaporative deposition and decomposition and (iv) plasma- and laser-induced reactions. 

The chemical vapor deposition processes obtained from the laser induced multiphoton decomposition of neat organogermanes or sensitized by SFg have also been characterized for several systems. For example, the decomposition of Ge(OMe)4 leads to the formation of organoxogermanium polymers, while EtOGeMcs leads to materials rich in Ge and containing small amounts of oxygen and carbon. In the latter case, two primary processes have been proposed to be responsible for the chain reactions leading to the final products (equations 40a and 40b)... 

The CO2 laser-induced multiphoton decomposition of silanes, known to be a really homogeneous reaction, was utilized for the chemical vapour deposition of fluorine containing SiC films from the parent (fluoromethyl)silanes [25, 26]. In contrast to work with H3CS1H3, irradiation of (fluoromethyl)silanes with a single unfocused CO2 laser pulse at fluence of S 0.9 Jcm" tuned to absorption bands of either the SiH bending or the CF stretching vibrations results in an explosive reaction. This is accompanied by an intense chemoluminescence when the sample pressure exceeds a certain limit in the range of 0.1-6.7 kPa (Fig. 1). 

In summary, mass-selected TOF measurements during the UV laser (248 nm)-induced decomposition of a photolabile polymer show fast neutral particles which are most likely due to particles emitted directly from the surface by a concerted, exothermal chemical reaction. At this point, time-of-flight measurements cannot distinguish whether this reaction is initiated directly by photon absorption (photochemical dissociation) or exothermic de-... 

Laser-induced, collision-induced, and metastable decomposition reactions of the larger cluster ions were examined with a triple-quadrupole mass spectrometer. Various phenomena observed during the decomposition of the clusters suggested four kinds of energy storage thermal, vibrational [N2(v=1)], electronic, and chemical. In smaller clusters (n<9) containing argon in the inner shell, two moles of N2 are lost via the reaction Ar+N N2 +ArNj, which is indicative for the chemical metastability of these clusters [36]. 

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