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Ciobotaru L.C.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Optoelectronics and Advanced Materials, Rapid Communications | Year: 2011

The paper deals with the Penning reactions role in the decreasing process of the dominant spectral lines number which appear in multiple noble gases-hydrogen mixtures in comparison with single noble gas-hydrogen mixture. These reactions could be considerate as a redistribution energy agent between the heavy particles (excited, ionized, neutral), involved in the monochromatisation -effect appearance.


Ciobotaru L.C.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Optoelectronics and Advanced Materials, Rapid Communications | Year: 2012

In electronegative-electropositive gas mixtures plasma, at a total pressure varying in the range of ten to hundred Torr, was reported the appearance of a quasi-mochromatization effect of the emitted radiation. This radiation could be the result of the generating mechanisms at molecular level, which is the case of the excimer radiation but also at atomic level. Thus, in the last case, in (Ne+1%Ar/Xe+H 2) gas mixtures plasma in a dielectric barrier discharge (DBD), this effect consists in the reduction of the discharge emission spectrum practice at one single, strong spectral line, namely = 585.3 nm. The present paper is concerned with the main characteristics comparative investigation of the principal reaction mechanisms involved in the quasi-monochromatization effect existence, namely the direct Harpoon reaction, in the case of the excimer radition, which appears as a result of the generation processes at molecular level and the resonant polar three-body reaction, as a result of the generation processes at atomic level. Also, the paper points out the role and the importance of the metastable electronegative atoms in the appearance of the monochromatization-effect at atomic level.


Ionel L.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Optoelectronics and Advanced Materials, Rapid Communications | Year: 2013

A spatio-temporal study in focal point of the distorted laser beam after propagation through an optical chirp pulse amplification (CPA) system was developed. This study is based on numerical simulation using the ray-tracing model from Rayica module of MATHEMATICA and it relates the spatial and temporal behavior of the distorted beam in focal region in case of user-induced misalignments in grating stretcher-compressor system. Consequently, the misalignments influence the focal structure of the electromagnetic distribution of the CPA laser beam. The results are relevant for different applications which use CPA systems with needs of high quality laser beam profile in focus.


Ciobotaru L.C.,Romanian National Institute for Lasers, Plasma and Radiation Physics
Romanian Reports in Physics | Year: 2010

The monochromatisation effect consists in the decrease of the emission spectra of an electronegative-electropositive gas mixture discharge to only few intense spectral lines or even one line, as in the case of Ne-H2 gas mixture (the so called M-effect). The paper presents the general aspect of this behavior wich is outlined for Ar+H2 and He+O2 gas mixtures discharges. The differences consist in the number of the dominant spectral lines appeared. Thus, at least two different dominant spectral lines were found to increase and give rise to the M-effect in an AC discharge. In a DC discharge, similar to the Ne-H2 gas mixture discharge, the appearance of one single intense spectral line is reported.


Bgldea I.,University of Heidelberg | Bgldea I.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Koppel H.,University of Heidelberg
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

A negative differential resistance (NDR) in nanotransport is often ascribed to electron correlations. We present a simple example revealing that finite electrode bandwidths and energy-dependent electrode density of states can cause a significant NDR, which may occur even in uncorrelated systems. So, special care is needed in assessing the role of electron correlations in the NDR. © 2010 The American Physical Society.

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