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The temporal evolution of electric breakdown in air at atmospheric pressure by Nd:yttrium–aluminum–garnet Q-switched nanosecond laser pulses was studied from the nanosecond to the millisecond time scale by shadowgraphy and interferometry techniques. The results were modeled with a gasdynamic code with good agreement. It was possible to simultaneously model the whole evolution of the plasma, the shock wave, and the hot core air. The shock wave velocity was determined to be ⩾60 km s−1 at 20 ns. The plasma temperature was found to reach about 1.7×104 K at 1 μs and the hot core air temperature was determined to be <103 K at 100 μs. This letter presents an experimental work that extends the study of laser induced plasmas to millisecond time scales.

This paper is part o f a more general study aimed to the determination o f the best experimental procedures for reliable quantitative measurements o f F e-M n alloys by LIBS. In this work, attention is pointed on the self-absorption processes, whose effect deeply influences the LIBS measurements, reflecting in non-

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Abstract.We report an experimental assessment of the contributions of the shockwave and the hot channel to the production of nitric oxide by simulated lightning. Lightning in the laboratory was simulated by a hot plasma generated with a pulsed Nd-YAG laser. The temporal evolution of electric breakdown in air at atmospheric pressure was studied from the nanosecond to the millisecond time scale by shadowgraphy and interferometry techniques. The shockwave front velocity was determined to be about 60 km s -x at 20 ns and the temperature behind the shock front was estimated to be about 105 K. The production yield of nitric oxide by shock heating is estimated to be: P(NO) (3 4-2) x 10 TM molecule J-• In contrast it was calculated that the production yield of NO by the hot channel is as much as P(NO) = (1.5 4-0.5) x 10 x7 molecule J-X To the extent our simulation is an accurate representation of natural lightning, the hot channel is the dominant region for nitrogen fixation.

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Binary metal-semiconductor Zn/ZnO core-shell nanorods have been synthesized through an ethylenediamine-assisted low-temperature hydrothermal process. Well-crystalline wurtzite phase ZnO was epitaxially grown along the [0100] direction, perpendicular to the single-crystalline Zn nanorod cores grown along the [0002] direction. The structure and optical properties of the binary metal-semiconductor nanostructures were studied by SEM, HRTEM, absorption, and emission spectroscopy techniques. The mechanisms for the growth of such binary structures in solution based synthesis are discussed. The growth technique can be extended for the preparation of other hybrid nanostructures.

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