The present work describes a systematic experimental investigation of a N 2 O hollow cathode discharge. The local electron mean energy and density have been determined with a double Langmuir probe. Fourier transform infrared spectroscopy and mass spectrometry have been employed for the measurement of the concentration of the stable species present in the discharge. N 2 O, N 2 , O 2 , and NO are always identified as the main constituents of the discharge plasma. In addition, NO 2 is found for the first time in a glow discharge of nitrous oxide. As a plausible explanation, a reaction of NO with oxygen atoms adsorbed on the cathode walls is proposed, although homogeneous reactions of vibrationally excited species cannot be discarded. A model based on a reduced set of kinetic equations including electron dissociation, gas-phase reactions, and gas-surface processes can give a global account of the measured data for all the experimental conditions used. The results are discussed and, when possible, compared to previous works on other types of N 2 O glow discharges.

Magnetic nanoparticles were generated by ultrashort pulsed laser ablation of an iron target in water, methanol, ethanol, acetone and toluene. The relationship between ablation rate, liquid properties and the physical and chemical properties of the nanoparticles was studied. Composition, morphology and magnetic properties were investigated by TEM, XPS and vibrating-sample (VSM) and SQUID magnetometry. The properties of the generated nanoparticle ensembles reflected the influence of the liquid environment on the particle formation process. For example, the composition was strongly dependent on the carbon to oxygen ratio within the molecules of the liquid. In contrast to short pulsed laser ablation in liquids, the nanoparticles generated by ultrashort pulses had a higher level of polycrystallinity.

The transition dipole moment of the v3 band of the methyl radical has been measured for the first time. A new discharge laser amplitude double modulation method with a difference frequency laser spectrometer and a hollow cathode discharge cell has been used. The CH3 concentration has been estimated from the absorption decay when the discharge is turned off. The transition dipole moment is found to be pv, = 0.029 f 0.005 D.

The present work describes the first experimental study of the transients involved in the turn on and off of a N2O hollow cathode discharge until the attainment of the respective stationary states. Time-resolved Fourier transform infrared spectroscopy and quadrupole mass spectrometry with ionization by electronic impact have been used to measure the temporal evolution of the concentrations of the stable species present in the discharge N2O, N2, O2, NO, and NO2. A model based on a reduced set of kinetic equations gives a global account of the measured data; this model takes into account all the mechanisms considered in a former work (Arcos, T. et al. J. Phys. Chem. A 1998, 102, 6282) to explain the steady state of a continuous N2O discharge but includes also additional mechanisms to which transient phenomena have proven to be much more sensitive than the stationary results. In particular, excitation of some vibrational levels of N2O and homogeneous reactions of vibrationally excited species, as well as electron impact dissociation of the stable products of the discharge are considered. On the other hand, the partial formation of NO2 by an heterogeneous reaction previously proposed seems to be confirmed.

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Experimental studies on a pulsed hollow cathode capillary discharge AIP Conf.Double modulationhigh resolution infrared spectroscopic technique: The ν3 band of the CH3 radical and excited states of CH4 in a hollow cathode discharge J. Chem. Phys. 100, 238 (1994); 10.1063/1.466991Mass spectroscopic investigation of the CH3 radicals in a methane rf discharge Appl.

In this work the changes in the infrared absorption of N 2 O observed in a hollow cathode discharge modulated by a 45 Hz square wave are studied by time-resolved infrared absorption spectroscopy, with a Fourier transform infrared (FTIR) spectrometer working in the step-scan mode. These variations are attributed to alternative population and depopulation of the ground state of N 2 O; on the other hand, no changes are observed in the total concentration of N 2 O and the major products of the discharge. The experimental results are explained by means of a simple kinetic model: vibrational excitation processes are assumed to be the main cause of the observed effects, but an inhomogeneous distribution of the stable species and the incorporation of diffusion terms between the plasma volume and the rest of the discharge cell are shown to be crucial in order to justify the quick and sharp variations in the N 2 O ground-state population seen along the path of the IR beam. The influence of these effects has been verified also by mass spectrometric measurements of the temporal behavior of the concentration of the major products N 2 O, N 2 and O 2 at one end of the discharge cell and at different frequencies.

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