A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:
Spatial emission distribution of a pulsed radiofrequency glow discharge: Influence of the pulse frequency
25 January 2012, 01:10:56
Publication year: 2012
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
Rebeca Valledor, Jorge Pisonero, Thomas Nelis, Nerea Bordel
A pulsed radiofrequency Glow Discharge (pulsed rf GD) plasma has been spectroscopically characterized by performing side-on measurements of the emitted radiation. The effect of varying the pulse frequency (e.g. between 100 and 10000 Hz), while keeping the duty cycle constant at 25%, has been investigated on different argon and analyte (i.e. copper) emission lines, at different plasma locations. In particular, it is observed that an intermediate frequency of 2.5 kHz favors the excitation of the argon atoms, while the argon ions are preferably excited by lower frequencies (e.g. longer pulse widths). Moreover, the excitation of copper atoms has a strong dependence on the upper energy level, and it has been noticed that the emission from higher levels is favored by the use of lower pulsed-rf frequencies. On the other hand, it has been found that the spatial distribution of the gas species and the analyte species (i.e. Ar and Cu, respectively) differ from each other: the atomic argon emission extends longer along the plasma plume than the atomic copper emission. Furthermore, ionic species have their maximum emission signal in the region close to the anode; however, their emission signal decay quite fast at increasing distances to the anode. Nevertheless, it should be highlighted that it is possible to detect ionic emission at distances far away from the negative glow; in regions where usually the sampler cone interface is placed in GD-MS instruments.
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
Rebeca Valledor, Jorge Pisonero, Thomas Nelis, Nerea Bordel
A pulsed radiofrequency Glow Discharge (pulsed rf GD) plasma has been spectroscopically characterized by performing side-on measurements of the emitted radiation. The effect of varying the pulse frequency (e.g. between 100 and 10000 Hz), while keeping the duty cycle constant at 25%, has been investigated on different argon and analyte (i.e. copper) emission lines, at different plasma locations. In particular, it is observed that an intermediate frequency of 2.5 kHz favors the excitation of the argon atoms, while the argon ions are preferably excited by lower frequencies (e.g. longer pulse widths). Moreover, the excitation of copper atoms has a strong dependence on the upper energy level, and it has been noticed that the emission from higher levels is favored by the use of lower pulsed-rf frequencies. On the other hand, it has been found that the spatial distribution of the gas species and the analyte species (i.e. Ar and Cu, respectively) differ from each other: the atomic argon emission extends longer along the plasma plume than the atomic copper emission. Furthermore, ionic species have their maximum emission signal in the region close to the anode; however, their emission signal decay quite fast at increasing distances to the anode. Nevertheless, it should be highlighted that it is possible to detect ionic emission at distances far away from the negative glow; in regions where usually the sampler cone interface is placed in GD-MS instruments.
Highlights
► Influence of frequency on the spatial emission distribution of pulsed-rf-GD-OES ► Ar emission is enhanced at intermediate pulse frequencies (2-3 KHz) ► Cu emission from energetic levels is favored at low frequencies (100 Hz) ► Cu emission from lower upper levels (< 4 eV) is enhanced at high frequency (10 KHz) ► Ion Cu population around sampler cone region close related to GD conditionsInfluence of nitrogen impurities on the population of plasma species in atmospheric-pressure helium microwave plasmas
25 January 2012, 01:10:56
Publication year: 2012
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
J. Muñoz, J. Margot, M.K. Benhacene-Boudam
The characteristics of a helium microwave plasma produced at atmospheric pressure have been studied by means of laser induced fluorescence and emission spectroscopy. The influence of nitrogen impurities on discharge parameters (electron density and gas temperature) has been studied together with the variation of the He metastable (2S and 2S) populations. A strong decrease of the He metastable densities for nitrogen concentrations as small as 1% was found. The dependence of the populations of nitrogen molecular and atomic species has been examined as a function of the electron density and nitrogen concentration in helium. Comparison with a theoretical model accounting for the presence of nitrogen in the discharge show that Penning ionization by both atomic and molecular nitrogen play an important role on the metastable quenching.
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
J. Muñoz, J. Margot, M.K. Benhacene-Boudam
The characteristics of a helium microwave plasma produced at atmospheric pressure have been studied by means of laser induced fluorescence and emission spectroscopy. The influence of nitrogen impurities on discharge parameters (electron density and gas temperature) has been studied together with the variation of the He metastable (2S and 2S) populations. A strong decrease of the He metastable densities for nitrogen concentrations as small as 1% was found. The dependence of the populations of nitrogen molecular and atomic species has been examined as a function of the electron density and nitrogen concentration in helium. Comparison with a theoretical model accounting for the presence of nitrogen in the discharge show that Penning ionization by both atomic and molecular nitrogen play an important role on the metastable quenching.
Highlights
► Influence of N2impurities (< 1%) on a He plasma was studied by FIL and OES. ► Small impact of N2impurities on electron density and gas temperature. ► A strong decrease of He metastable density upon N2introduction was found. ► Penning ionization of nitrogen produces He quenching.The effect of sample temperature on the emission line intensification mechanisms in orthogonal double-pulse Laser Induced Breakdown Spectroscopy
25 January 2012, 01:10:56
Publication year: 2012
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
R. Sanginés, H. Sobral, E. Alvarez-Zauco
Orthogonal double-pulse laser ablation on aluminum-based alloy target at atmospheric pressure was investigated by time-resolved optical emission spectroscopy. Studies were performed as a function of the distance from the first pulse plasma induced in air to the sample surface. Double-pulse experimental results were compared to single-pulse laser ablation experiments carried out in a heated target to up to 500 °C. Emission lines intensification mechanisms are discussed in terms of the sample heating by the pre-ablation pulse. Crater volume was also determined via confocal microscopy for both, double pulse and target heating, experiments. It was found that the emission intensification is mainly due to an enhancement of the ablated mass. The mechanisms for the mass removal increasing are discussed.
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
R. Sanginés, H. Sobral, E. Alvarez-Zauco
Orthogonal double-pulse laser ablation on aluminum-based alloy target at atmospheric pressure was investigated by time-resolved optical emission spectroscopy. Studies were performed as a function of the distance from the first pulse plasma induced in air to the sample surface. Double-pulse experimental results were compared to single-pulse laser ablation experiments carried out in a heated target to up to 500 °C. Emission lines intensification mechanisms are discussed in terms of the sample heating by the pre-ablation pulse. Crater volume was also determined via confocal microscopy for both, double pulse and target heating, experiments. It was found that the emission intensification is mainly due to an enhancement of the ablated mass. The mechanisms for the mass removal increasing are discussed.
Highlights
► Emission enhancement in orthogonal double pulse (DP) LIBS were investigated. ► DP-LIBS results were compared to single pulse LIBS onto a heated target. ► Target heating produced by the air plume contributes to DP emission intensification.Expansion and backscattering of laser produced Fe plasma plume
25 January 2012, 01:10:56
Publication year: 2012
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
M. Bišćan, S. Milošević
Forward and backward moving atoms within the laser produced plasma plume were studied by means of a cavity ringdown spectroscopy. The plume was produced using a nanosecond Nd-YAG laser pulse illuminating stainless steel target in a vacuum or helium background gas. Measurements were done at pressures ranging from 10to 1 mbar. Atomic absorption line shapes of iron around 388 nm were measured above and below the target at different times after the ablation initiation. Changes in absorption line shapes were used to estimate kinetic parameters of the plasma plume. The observations were interpreted through modeling which takes into account the angular and velocity distributions of atoms in the expanding plume. The amount of backward scattered atoms was about 10% of the total number of particels.
Source: Spectrochimica Acta Part B: Atomic Spectroscopy, Available online 24 January 2012
M. Bišćan, S. Milošević
Forward and backward moving atoms within the laser produced plasma plume were studied by means of a cavity ringdown spectroscopy. The plume was produced using a nanosecond Nd-YAG laser pulse illuminating stainless steel target in a vacuum or helium background gas. Measurements were done at pressures ranging from 10to 1 mbar. Atomic absorption line shapes of iron around 388 nm were measured above and below the target at different times after the ablation initiation. Changes in absorption line shapes were used to estimate kinetic parameters of the plasma plume. The observations were interpreted through modeling which takes into account the angular and velocity distributions of atoms in the expanding plume. The amount of backward scattered atoms was about 10% of the total number of particels.
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