J.L. Le Garrec

Experimental studies of cold electron attachment to SF6, CF3Br, and CCl2F2

A new technique has been used for the measurement of electron attachment rate coefficients for the molecules, SF6, CF3Br, and CCl2F2 at temperatures between 48 and 170 K. The results demonstrate very clearly the strong effect that internal vibrational energy of the molecules has on the attachment process.

In-situ small-angle x-ray scattering study of nanoparticles in the plasma plume induced by pulsed laser irradiation of metallic targets

Small angle x-ray scattering was used to probe in-situ the formation of nanoparticles in the plasma plume generated by pulsed laser irradiation of a titanium metal surface under atmospheric conditions. The size and morphology of the nanoparticles were characterized as function of laser irradiance. Two families of nanoparticles were identified with sizes on the order of 10 and 70 nm, respectively. These results were confirmed by ex-situ transmission electron microscopy experiments.

Branching ratios for the dissociative recombination of hydrocarbon ions. I: The cases of C4H9+ and C4H5+

Abstract Branching ratios for CC bond breaking during the dissociative recombination of C4H9+ and C4H5+ ions, produced from n-butane gas in a Nielsen source, have been measured using the merged beam method at the ASTRID storage ring. These results show that while C4H9+ recombines to form C4 and C3+C products, C4H5+ recombines to form C4 and C2+C2 products. A discussion of how these fragmentation patterns may be related to the isomeric forms of the ions undergoing recombination is presented.

Electron and ion reactions with hexamethyldisiloxane and pentamethyldisiloxane

The dissociative recombination of electrons with the hexamethyldisiloxane (HMDSO) cation ((CH(3))(3)Si-O-Si(CH(3))(3))(+) and the pentamethyldisiloxane cation ((CH(3))(3)Si-O-Si(CH(2))(2))(+) as well as the ion-molecule reaction between Ar(+) and HMDSO have been studied at 300 K using a flowing afterglow Langmuir probe-mass spectrometer apparatus. The rate constants for these reactions, measured directly for the first time, are, respectively, alpha(1)=1.8 x 10(-6), alpha(2)=3.6 x 10(-6) cm(3)s, and k=2.0 x 10(-9) cm(3)s with uncertainties of +/-30%. In addition, the electronic attachment to neutral HMDSO was also studied and an upper limit value of the rate constant was determined to be beta=3.3 x 10(-11) cm(3)s.

Reactions of Electrons with Hydrocarbon Cations: From Linear Alkanes to Aromatic Species

In the framework of our systematic study of the recombination of hydrocarbon ions, we have already obtained results for classical aliphatic carbocations,1 small unsaturated rings2 and methyl substituted benzenic rings.3 The recombination rate constants of these ions range from 5 to 12 × 10−7 cm3s−1 and are independent of the number of carbon atoms or structure.

THE TEMPERATURE DEPENDENCE OF THE RATE CONSTANT FOR O+ + NO NO++ O FROM 23 TO 30000 K

Abstract The rate constant, k, for the charge transfer reaction O+ + NO+ +_O, known to be slow at 300 K (8 × 10−13 cm3s−1) and to increase with relative kinetic energy (or temperature, T) to 2 × 10−10 cm3 s−1 at 30000 K, has been measured down to 23 K. The results show that k also increasesa t low T (3.2 × 10−11 cm s−1 at 23 K) which is interpreted as being due to the formation of a long-lived complex in which electronic state curve crossings occur.

Branching ratios for the dissociative recombination of hydrocarbon ions

Branching ratios for the recombination of hydrocarbon ions have been measured using the ASTRID storage ring electron cooler. These studies have concentrated upon the competition of channels where the carbon skeleton of the molecule is left intact with other channels where carbon-carbon bonds are broken. A discussion of the effects of initial molecular structure on the resulting dissociation pattern is given.

Particle size determination in electrical arcs with Ag and AgSnO2 electrodes using X-ray scattering

This article discusses recent synchrotron radiation based measurements of nanoparticle formation between arcing contacts. The studied material is typical in contact applications, Ag and AgSnO2.

Particle Size Determination in Electrical Arcs Using X-Ray Scattering

This article discusses recent synchrotron radiation based measurements of nanoparticle formation between arcing contacts.