He-N2 radiofrequency discharge: Influence of N2 on discharge and afterglow

A diagnostic study q (energy transfer processes in a He-N₂ flowing discharge and afterglow has been performed in a radiofrequency-produced plasma cooled in a liquid nitrogen hath. Optical emission spectroscopy in the visible and infrared spectral range as well as Langrnuir probe diagnostics were used. The vibrational kinetics of CO injected in such an afterglow has been examined. It shows a slow cooling of the electrons in the afterglow regime. The electron kinetics responsible joy CO vibrahonal excitation is turned off when N₂ is added to the He discharge, while that for vibrationally excited N₂ molecules is turned on. The results are discussed on the basis of previous theorerical calculations and experiments on the He-N₂ system.     

Nitrogen optical emission during nanosecond laser ablation of metals: prompt electrons or photo-ionization?

Experiments on the interaction of metal targets with a Nd:YAG laser beam ( \(\lambda \)  = 1,064 nm, intensity \(10^{10}\) – \(10^{11}\,\hbox {W/cm}{^2}\) ) are carried out in a finite Nitrogen pressure environment. The observed \(\hbox {N}_2\) spectra are unambiguous evidence of the existence of an ionization and excitation source, arriving at the observation volume prior to the plume. Such a source can be either prompt electrons or VUV radiation. The analysis reveals that the prompt electron interpretation requires energies in excess of 1 keV, incompatible with any acceleration mechanisms relevant for such laser intensities. On the other hand, VUV radiation is sufficiently strong to explain the observed spectra.     

New laser-induced fluorescence scheme for simultaneous OH and NO detection by a single laser set-up

In this communication, we propose a new laser-induced fluorescence (LIF) scheme that allows the simultaneous detection of OH and NO by a single laser set-up. OH is detected by the second harmonic (SH) of a dye laser tuned to the (0,0)-band of the 3064 ? system, while its third harmonic (TH) is used to detect NO through excitation of the (2,0)-band of the γ system. This scheme is presented and discussed within the framework of its potential use in field instruments for the measurement of tropospheric OH concentration. Received: 8 March 2002 / Revised version: 22 April 2002 / Published online: 8 August 2002     

On the Measurement of N2(A3Σ u + ) Metastable in N2 Surface-Dielectric Barrier Discharge at Atmospheric Pressure

The N₂(A³Σ _u ⁺ ) metastable has been investigated in an AC surface dielectric barrier discharge (surface-DBD) at atmospheric pressure in N₂ by Optical–Optical Double Resonance–Laser Induced Fluorescence spectroscopy (OODR-LIF) and by Optical Emission Spectroscopy (OES). The discharge is single-side produced by metallic stripes (comb-like electrode on a dielectric layer). The OODR-LIF measurements have been carried out in space afterglow above the plasma layer. The measurement was time resolved during the AC high voltage cycle and space resolved around the metallic/dielectric stripes. The space afterglow N₂(A) density does not evidence significant variation in the voltage cycle. The density is higher above the dielectric strip than on the metallic one. N₂(A) density in the space afterglow has been estimated to be about 10¹¹ cm^?3. The plasma layer, not accessible by OODR-LIF, has been investigated by OES through NOγ and Herman infrared bands. The estimated N₂(A) maximum density in the plasma layer is higher than 10¹² cm^?3.     

On the Use of the Numerical Simulation of the First Positive System of N2: I. Emission and LIF Analysis

Plasma Chemistry and Plasma Processing - Numerical modeling of the first positive system of N2 (B3Πg-A3Σu+ has been applied to analyze the plasma-induced emission and the laser-induced...