Search

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivsLicense, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made., This study presents experimental results for the radial and temporal variation of neutral and ion spectroscopic signatures emerging from the heated channel of lightning-like discharges diagnosed with a high speed (900,000 fps) imaging spectrograph. Light emissions emanate from three regions: an inner core (up to ∼2 mm), an external sheath (up to ∼4 mm) featuring a sudden temperature increase, and further optical emissions forming a dim glow from 4 mm up to 16 mm. The optical emissions are initially (, This work has received funding from the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement SAINT 722337. Additionally, this work was supported by the Spanish Ministry of Science and Innovation, MINECO, under project PID2019-109269RB-C43 and FEDER program. M. Passas-Varo, F. J. Gordillo-Vázquez, J. Sánchez, and N. Kieu acknowledge financial support from the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa's award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709).

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., How lightning initiates inside thunderclouds remains a major puzzle of atmospheric electricity. By monitoring optical emissions from thunderstorms, the Atmosphere-Space Interactions Monitor (ASIM) onboard the International Space Station is providing new clues about lightning initiation by detecting Blue LUminous Events (BLUEs), which are manifestations of electrical corona discharges that sometimes precedes lightning. Here we combine optical and radio observations from a thunderstorm near Malaysia to uncover a new type of event containing multiple optical and radio pulses. We find that the first optical pulse coincides with a strong radio signal in the form of a Narrow Bipolar Event (NBE) but subsequent optical pulses, delayed some milliseconds, have weaker radio signals, possibly because they emanate from a horizontally oriented electrical discharges which does not trigger full-fledged lightning. Our results cast light on the differences between isolated and lightning-initiating electrical discharges. © 2022. The Authors., This work was supported by the European Research Council (ERC) under the European Union H2020 programme/ERC grant agreement 681,257. The project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement SAINT 722337. Additionally, this work was supported by the Spanish Ministry of Science and Innovation, MINECO, under the project PID2019-109269RB-C43 and FEDER program. D.L., A.L. and F.J.G.V. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). G.L. and H.Z. are supported by the CAS Project of Stable Support for Youth Team in Basic Research Field (YSRR-018), the Chinese Meridian Project, and the International Partnership Program of Chinese Academy of Sciences (183311KYSB20200003).

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes., We present nighttime worldwide distributions of key features of Blue LUminous Events (BLUEs) detected by the Modular Multispectral Imaging Array of the Atmosphere-Space Interaction Monitor. Around 10% of all detected BLUEs exhibit an impulsive single pulse shape. The rest of BLUEs are unclear (impulsive or not) single, multiple or with ambiguous pulse shapes. BLUEs exhibit two distinct populations with peak power density, ASIM is a mission of ESA's SciSpace programme for scientific utilization of the ISS and non-ISS space exploration platforms and space environment analogues. ASIM and the ASIM Science Data Centre are funded by ESA and by national grants of Denmark, Norway, and Spain. This work was supported by the Spanish Ministry of Science and Innovation under project PID2019-109269RB-C43 and the FEDER program. SS acknowledges a PhD research contract through the project PID2019-109269RB-C43. FJPI acknowledges the sponsorship provided by Junta de Andalucía under Grant POSTDOC-21-00052. AL and DL were supported by the European Research Council (ERC) under European Union H2020 programme/ERC grant agreement 681257. SS, FJGV, AL, and DL acknowledge financial support from the State Agency for Research of the Spanish MCIU through the ”Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709).

In this work we present the first parameterizations of the global occurrence rate and chemical influence of Blue Jets, a type of transient luminous event taking place in the stratospheric region above thunderclouds. These parameterizations are directly coupled with five different lightning parameterizations implemented in the Whole Atmosphere Community Climate Model (WACCM4). We have obtained a maximum Blue Jet global occurrence rate of about 0.9 BJ per minute. The geographical occurrence of Blue Jets is closely related to the chosen lightning parameterization. Some previously developed local chemical models of Blue Jets predicted an important influence onto the stratospheric concentration of N2O, NOx, and O3. We have used these results together with our global implementations of Blue Jets in WACCM4 to estimate their global chemical influence in the atmosphere. According to our results, Blue Jets can inject about 3.8 Tg N2O-N/year and 0.07 Tg NO-N/year near the stratosphere, where N2O-N and NO-N stand for the mass of nitrogen atoms in N2O and NO molecules, respectively. These production rates of N2O and NOx could have a direct impact on, for example, the acidity of rainwater or the greenhouse effect. We have found that Blue Jets could also slightly contribute to the depletion of stratospheric ozone. In particular, we have estimated that the maximum difference in the concentration of O3 at 30 km of altitude between simulations with and without Blue Jets can be about −5% in equatorial and polar regions. ©2019. American Geophysical Union. All Rights Reserved., This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects and ESP2017-86263-C4-4-R and by the EU through the H2020 Science and Innovation with Thunderstorms (SAINT) project (Ref. 722337) and the FEDER program. Authors F.J.P.I and F.J.G.V acknowledge financial support from the State Agency for Research of the Spanish MCIU through the >Center of Excellence Severo Ochoa> award for the Instituto de Astrofisica de Andalucia(SEV-2017-0709). The National Center for Atmospheric Research is sponsored by the National Science Foundation. The CESM project is supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy. Computing resources were provided by the Climate Simulation Laboratory at NCAR's Computational and Information Systems Laboratory (CISL), sponsored by the National Science Foundation and other agencies. F. J. P.-I. acknowledges a PhD research contract, code BES-2014-069567. F. J. G.-V. acknowledges support from the Spanish Ministry of Education and Culture under the Salvador de Madariaga program PRX17/00078.

In this work, we develop two spectroscopic diagnostic methods to derive the peak reduced electric field in transient luminous events (TLEs) from their optical signals. These methods could be used to analyze the optical signature of TLEs reported by spacecraft such as Atmosphere-Space Interactions Monitor (European Space Agency) and the future Tool for the Analysis of RAdiations from lightNIngs and Sprites (Centre National d'Études Spatiales). As a first validation of these methods, we apply them to the predicted (synthetic) optical signatures of halos and elves, two types of TLEs, obtained from electrodynamical models. This procedure allows us to compare the inferred value of the peak reduced electric field with the value computed by halo and elve models. Afterward, we apply both methods to the analysis of optical signatures of elves and halos reported by Global LIghtning and sprite MeasurementS (Japan Aerospace Exploration Agency) and Imager of Sprites and Upper Atmospheric Lightning (National Space Organization) spacecraft, respectively. We conclude that the best emission ratios to estimate the maximum reduced electric field in halos and elves are the ratio of the second positive system of N to first negative system (FNS) of N (Formula presented.), the first positive system of N to FNS of N (Formula presented.) and the Lyman-Birge-Hopfield band of N to FNS of N (Formula presented.). In the case of reduced electric fields below 150 Td, we found that the ratio of the second positive system of N to first positive system of N can also be used to reasonably estimate the value of the field. Finally, we show that the reported optical signals from elves can be treated following an inversion method in order to estimate some of the characteristics of the parent lightning. ©2018. American Geophysical Union. All Rights Reserved., This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects ESP2015-69909-C5-2-R and ESP2017-86263-C4-4-R and by the EU through the H2020 Science and Innovation with Thunderstorms (SAINT) project (Ref. 722337) and the FEDER program. F. J. P. I. acknowledges a PhD research contract, code BES-2014-069567. A. L. was supported by the European Research Council (ERC) under the European Union H2020 programme/ERC grant agreement 681257. T.A. was supported by JSPS KAKENHI Grant 24840040. The simulation data presented here are available from figshare repository at https://figshare.com/s/f1c9f6c7bc728d6669dd.JEM-GLIMS and ISUAL data presented in this study are available in the webpages http://www.ep.sci.hokudai.ac.jp/similar to jemglims/index-e.html and http://formosat.tw/nspo_esok/, respectively.

This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects ESP2013-48032-C5-5-R, FIS2014-61774-EXP, and ESP2015-69909-C5-2-R and by the EU through the FEDER program. F.J.P.I. acknowledges a MINECO predoctoral contract, code BES-2014-069567. A.L. acknowledges support by a Ramon y Cajal contract, code RYC-2011-07801

This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects ESP2013-48032-C5-5-R, FIS2014-61774-EXP, and ESP2015-69909-C5-2-R and by the EU through the FEDER program. F.J.P.I. acknowledges a MINECO predoctoral contract, code BES-2014-069567. A.L. acknowledges support by a Ramon y Cajal contract, code RYC-2011-07801.

Halos and elves are Transient Luminous Events (TLEs) produced in the lower ionosphere as a consequence of lightning-driven electromagnetic fields. These events can influence the upper-atmospheric chemistry and produce optical emissions. We have developed different two-dimensional self-consistent models that couple electrodynamical equations with a chemical scheme to simulate halos and elves produced by vertical cloud-to-ground (CG) lightning discharges, Compact Intra-cloud Discharges (CIDs) and Energetic In-cloud Pulses (EIPs). The optical emissions from radiative relaxation of excited states of molecular and atomic nitrogen and oxygen have been calculated. We have upgraded previous local models of halos and elves to calculate for the first time the vibrationally detailed optical spectra of elves triggered by CIDs and EIPs. According to our results, the optical spectra of elves do not depend on the type of parent lightning discharge. Finally, we have quantified the local chemical impact in the upper atmosphere of single halos and elves. In the case of the halo, we follow the cascade of chemical reactions triggered by the lightning-produced electric field during a long-time simulation of up to one second. We obtain a production rate of NO molecules by single halos and elves of 10$^{16}$ and 10$^{14}$ molecules/J, respectively. The results of these local models have been used to estimate the global production of NO by halos and elves in the upper atmopshere at $\sim10^{-7}$ Tg~N/y. This global chemical impact of halos and elves is seven orders of magnitude below the production of NO in the troposphere by lightning discharges.

While lightning activity in Venus is still controversial, its existence in Jupiter and Saturn was first detected by the Voyager missions and later on confirmed by Cassini and New Horizons optical recordings in the case of Jupiter, and recently by Cassini on Saturn in 2009. Based on a recently developed 3-D model, we investigate the influence of lightning-emitted electromagnetic pulses on the upper atmosphere of Venus, Saturn, and Jupiter. We explore how different lightning properties such as total energy released and orientation (vertical, horizontal, and oblique) can produce mesospheric transient optical emissions of different shapes, sizes, and intensities. Moreover, we show that the relatively strong background magnetic field of Saturn can enhance the lightning-induced quasi-electrostatic and inductive electric field components above 1000 km of altitude producing stronger transient optical emissions that could be detected from orbital probes.©2017. American Geophysical Union. All Rights Reserved., This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects ESP2013-48032-C5-5-R, ESP2015-69909-C5-2-R, and FIS2014-61774-EXP and by the EU through the FEDER program. F.J.P.I. acknowledges a PhD research contract, code BES-2014-069567. A.L. was supported by the European Research Council (ERC) under the European Union's H2020 programme/ERC grant agreement 681257.

We investigate the attenuation of whistler waves generated by hypotetical Venusian lightning occurring at the altitude of the cloud layer under different ionospheric conditions. We use the Stanford full-wave method for stratified media of Lehtinen and Inan (2008) to model wave propagation through the ionosphere of Venus. This method calculates the electromagnetic field created by an arbitrary source in a plane-stratified medium (i.e., uniform in the horizontal direction). We see that the existence of holes in electronic densities and the magnetic field configuration caused by solar wind play an important role in the propagation of electromagnetic waves through the Venusian ionosphere. ©2017. American Geophysical Union. All Rights Reserved., This work was supported by the Spanish Ministry of Science and Innovation, Ministerio de Economia y Competitividad (MINECO) under projects ESP2015-69909-C5-2-R and FIS2014-61774-EXP, by the Research Council of Norway under contracts 208028/F50, 216872/F50, and 223252/F50 (CoE), and by the EU through the FEDER program. F. J. P. I. acknowledges a PhD research contract, code BES-2014-069567. N. L. was supported by the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement 320839. A. L. was supported by the European Research Council (ERC) under the European Union's H2020 program/ERC grant agreement 681257.

We report a technique that is able to achieve high spatial resolution in the measurement of the temporal and spectral emission characteristics of laser-induced expanding plasmas. The plasma is imaged directly onto the slit of an imaging spectrograph coupled to a time-gated intensified camera, with the plasma expansion direction being parallel to the slit extension. In this way, a single hybrid detection system is used to acquire the spatial, spectral and temporal characteristics of the laser induced plasma. The parallel acquisition approach of this technique ensures a much better spatial resolution in the expansion direction, reproducibility and data acquisition speed than commonly obtained by sequential measurements at different distances from the target. We have applied this technique to study the laser-induced plasma in LiNbO3 and Bi12Ge1O20, revealing phenomena not seen in such detail with standard instruments. These include extreme line broadening up to a few nanometers accompanied by self-absorption near the target surface, as well as different ablation and expansion dynamics for the different species ejected. Overall, the high precision and wealth of quantitative information accessible with this technique open up new possibilities for the study of fundamental plasma expansion processes during pulsed laser ablation. © 2005 Elsevier B.V. All rights reserved., This work was partially funded by CICYT (Spain), under Project TIC 2002-03235 and by European Union under Project HPRN-CT-2002-00328.

We have used a kinetic model to investigate the influence of changing the pressure (0.1–0.8 Torr) and power (100–300 W) on the non-equilibrium plasma chemistry of RF (13.56 MHz) produced C2H2 (1%)/H2/Ar plasmas of interest for the synthesis of nanodiamond thin films. We found that the concentrations of the species , C2 (a 3Πu) and C2H are not sensitive to variations in the power but they exhibit a significant increase when the pressure decreases at high argon content in the plasma. In addition, the concentrations of C2H2, CH4 and CH3 exhibit a slight (case of C2H2) or negligible (case of CH3 and CH4) power-dependence although they decrease (case of C2H2 and CH4) or remain almost constant (case of CH3) as the pressure decreases. A reasonable agreement is found when comparing the model predictions with available experimental results. These findings provide a basic understanding of the plasma chemistry of hydrocarbon/Ar-rich plasma environments and, at the same time, can be of interest to optimize the processing conditions of nanodiamond films from medium pressure RF hydrocarbon/Ar-rich plasmas.

A new formulation is presented for the calculation of effective dielectric magnitudes of two-component composites in which both components (the host matrix particles and the embedded particles) exhibit nonlinear behaviour of the Kerr type. It is predicted that, under certain conditions, two nonlinear component composites can exhibit optical bistable behaviour as a function of the shape and concentration of the embedded particles, the dielectric contants of the components, the intensity of the external electric field (power density) and the intrinsic third-order nonlinear optical susceptibilities χ(3) p and χ(3) m of the nonlinear components. It is also deduced that, as the power density increases, the effective third-order nonlinear optical susceptibility χ(3) of the composite exhibits a clear transition from values close to χ(3) p (low power density) to χ(3) m (high power density). Therefore, it is shown that the optical response of binary composites dramatically changes at moderate and high pow...

An analytic kinetic model is elaborated to determine the spatial evolution of the concentration of ground and excited Li atoms (up to the 3 2D level) present in the plasma generated by pulsed laser ablation of a LiNbO3 crystal in gas atmospheres (at 1 Torr) of different nature, both reactive (O2) and inert (Ar). Whereas the Li atom population densities in the plasma produced in gas are, in general, higher than those found in vacuum, the concentration of ground Li atoms close to the substrate is similar in vacuum and Ar, though lower than in O2. It is suggested that the reabsorption of radiation by the plasma is more important within O2 than in Ar since the absorber (ground Li) concentration is higher in O2 environments. A very reasonable qualitative agreement is found when comparing the Li I-670.8 nm spectral line emission intensity predicted by the model with that obtained experimentally in Ar and O2 atmospheres.

The influence of gas atmospheres (at 1 torr) of different natures, both reactive (O2) and inert (Ar), on the spatial evolution of the electron temperature (Te) and electron density (Ne) of the plasma generated by laser ablation of a LiNbO3 target is evaluated by optical emission spectroscopy techniques. It is found that the behavior of Ne in the plasma produced in vacuum, argon, and oxygen atmospheres exhibit quite different trends as a function of the distance from the target to the substrate, but the behavior of Te is nearly constant. The spatial constancy of Te in all the atmospheres studied is probably related not only to the low laser irradiance used (0.06 GW cm-2), but also to a possible collisional decoupling of the heavy species in the central part of the expanding plasma plume where a low pressure region is formed. The fact that Ne is lower in Ar than in O2 indicates the presence of fewer positive ions in the plasma generated in Ar. The impact of this result on the better crystallinity observed in the LiNbO3 films grown in Ar is also discussed. © 2002 Society for Applied Spectroscopy, This work was partially funded by CICYT (Spain) under Project No. TIC99-0866 and by MCYT under a Ramón y Cajal Project. F.J.G.-V. acknowledges a contract from the Spanish Ministry of Education and Culture (MEC).

PumpKin is a software package to find all principal pathways, i.e. the dominant reaction sequences, in chemical reaction systems. Although many tools are available to integrate numerically arbitrarily complex chemical reaction systems, few tools exist in order to analyze the results and interpret them in relatively simple terms. In particular, due to the large disparity in the lifetimes of the interacting components, it is often useful to group reactions into pathways that recycle the fastest species. This allows a researcher to focus on the slow chemical dynamics, eliminating the shortest timescales. Based on the algorithm described by Lehmann (2004), PumpKin automates the process of finding such pathways, allowing the user to analyze complex kinetics and to understand the consumption and production of a certain species of interest. We designed PumpKin with an emphasis on plasma chemical systems but it can also be applied to atmospheric modeling and to industrial applications such as plasma medicine and plasma-assisted combustion. Program Summary Program title: PumpKin Catalogue identifier: AETG_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AETG_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 18753 No. of bytes in distributed program, including test data, etc.: 7011133 Distribution format: tar.gz Programming language: C + + . Computer: All computers with a C/C + + compiler. Operating system: All platforms with a C/C + + compiler. Classification: 16.12, 16.14, 19.11, 19.8. External routines: GLPK (GNU linear programming kit) Nature of problem: Analyzing complex chemical models. Solution method: Combining reactions into pathways that recycle short-lived species Running time: Runtime depends on the input files sizes and user’s configuration. For typical use cases we estimate runtime in the order of minutes.

An analytic kinetic model capable to predict the spatial and temporal evolution of the population densities of ground and excited state Li atoms (up to the 32D level) in nonequilibrium laser-generated plasmas from LiNbO3 targets is presented. The model is especially useful as a nonequilibrium diagnostic tool for determining the concentrations of Li atoms from available measurements of electron density (Ne) and temperature (Te). In addition, the present approach is able to determine the electron kinetic mechanisms contributing to populate and depopulate the Li atom ground and excited states in laser-produced plasmas. A very reasonable qualitative agreement is found when comparing the model predicted Li atom densities with those obtained experimentally. Thus, the proposed approach can be used as a useful tool to optimize the processes involved in pulsed laser deposition of LiNbO3 thin films.

A nonlinear collisional-radiative model is used for a non-equilibrium, stationary argon plasma. The model includes three atomic energy levels: the ground level, one excited level and the continuum. A Maxwellian electron energy distribution function is also assumed. The model is solved for the electron and excited atom densities in two plasma regimes; with and without diffusion losses. A linear stability analysis is performed for both regimes. The maintenance electric field intensity and the average power loss per electron are obtained as a function of the electron number density for high-frequency discharges. The results of the calculations are discussed in a low (0.28, 1.1 and 2.8 Torr) and an intermediate (6.0 and 10.0 Torr) gas pressure range.

The stability of the general analytical solutions of a collisional‐radiative model, for nonequilibrium, partially ionized, steady‐state argon plasma, is examined. The model includes three atomic energy levels: the ground level, one excited level, and the continuum. A Maxwellian electron distribution function is also assumed. This model was previously considered by Braun and Kunc [Phys. Fluids 30, 671 (1987)]. All the rates for collisional‐radiative processes and diffusion losses are expressed as analytical functions. The model is solved for the electron and excited atom densities in two plasma regimes, with and without diffusion losses. Transitions between these two possibilities are also discussed.

Emission spectroscopy is used to determine the spatial and temporal evolution of the electronic temperature (Te) and density (Ne) of the plasma generated by laser ablation in vacuum of a LiNbO3 target. It is found that whereas Ne (in the range of 1016 cm−3) decreases by a factor of 2 as the distance to the target surface increases 10 mm, Te (in the range 0.7–0.8 eV) only decreases 10% between 2 and 4 mm from the target to remain nearly constant for longer distances. While Te is almost constant in time at the studied distances, Ne presents a maximum at a time delay that increases when increasing the distance to the target surface. The space–time constancy of Te is related to a collisional decoupling of the heavy species in the plasma for distances longer than 2–4 mm.

[Full-text paper not available yet], A unique formulation is presented to derive the spectral representation function of heterogeneous two-component materials in terms of an expansion on Legendre polynomials. This approach notably simplifies the calculations needed to estimate the effective dielectric function from the spectral density function and allows one to extract it from experimental data by using quite simple analytic expressions. The spectral representation function derived by the present method agrees notably well with experimental infrared reflectance measurements obtained from several ionic compounds. In addition, we state that the infrared spectral region is the optimal one in order to determine the full relationship between the spectral density function and the effective dielectric constant of a composite material., F.J.G-V. acknowledges partial support by CSIC-CAM (under project 200550M016) and C.P. acknowledges the EU IP NANOKER project FP6-515784-2.

3 pags. ; 4 figs., Optical emission spectroscopy is used to investigate the spatial evolution of the electron temperature (Te) and electron density (Ne) in the plasma generated by laser ablation in a vacuum of a wide-band-gap material, such as LiF, with a pulsed 193 nm excimer laser operating at a fluence of 1.5 J cm⁻² close to the threshold. It is found that, whereas Ne (in the range of 10¹⁶ cm⁻³) decreases by a factor of 2 as the distance to the target increases, Te exhibits a sharp decrease (from 1.85 eV to 0.66 eV) between 1 and 2 mm from the target and it remains practically constant for longer distances from the target. These results provide direct measurements of the electron temperature and density during nanosecond laser ablation of LiF., This work was partially funded by CICYT sSpaind, under Project No. TIC2002-03235. One of the authors sA.P.M.d acknowledges the E. U. for financial support from a Marie Curie Host Fellowship allowing a training period of 9 months at the Instituto de Óptica (CSIC) in Madrid sLASYNTHASS Project, Ref. No. HPMT-CT-2000-00064d.

We report a hybrid imaging technique capable of performing measurements of the spatial, temporal, and spectral emission characteristics of laser-induced plasmas by use of a single detection system. We apply this technique to study the plasma produced by laser ablation of LiNbO3 and observe phenomena not seen in such detail with standard instruments. These include extreme line broadening up to a few nanometers accompanied by self-absorption near the target surface, and expansion dynamics that differ strongly between the different species. Overall, the wealth of quantitative information provided by this novel technique sheds new light on processes occurring during plasma expansion. © 2004 Optical Society of America., G. Epurescu acknowledges funding by the European Union (HPRN-CT-2000-00160).

6 pages, 5 figures, 6 tables., We show that the concentrations of the species C2 (X 1Σg+), C2 (a 3Πu), and C2H exhibit a significant increase when the argon content grows up to 95% in medium pressure (0.75 Torr) radio frequency (rf) (13.56 MHz) produced C2H2 (1%)/H2/Ar plasmas of interest for the synthesis of nanodiamond thin films within plasma enhanced chemical vapor deposition devices. In contrast, the concentrations of CH3 and C2H2 remain practically constant. The latter results have been obtained with an improved quasianalytic space–time-averaged kinetic model that, in addition, has allowed us to identify and quantify the relative importance of the different underlying mechanisms driving the nonequilibrium plasma chemistry of C2. The results presented here are in agreement with recent experimental results from rf CH4/H2/Ar-rich plasmas and suggest that the growth of nanodiamond thin films from hydrocarbon/Ar-rich plasmas is very sensitive to the contribution of C2 and C2H species from the plasma., This work was partially funded by CICYT (Spain) under a Ramón y Cajal project and under Project No. TIC2002- 03235. One of the authors (F.J.G.V.) acknowledges a Ramón y Cajal contract from the Spanish Ministry of Science and Technology (MCYT). One of the authors (J.M.A.) acknowledges partial support from CICYT (Spain) under Project No. MAT 2002-04085-C02-02.

We have derived an analytic approach, based on the hypothesis of the effective-medium theory, to evaluate the effective dielectric magnitudes, including the effective third order nonlinear optical susceptibility 〈χ(3)〉, of a heterogeneous two-component medium in which one of the components (the host matrix or the embedded particle respectively) presents nonlinear behaviour. Our formulation allows us to solve the full nonlinear problem in the whole range of concentrations without treating the nonlinear effects as a small perturbation to the linear behaviour. Therefore, it can be considered as an upper limit of the commonly used low-field nonlinear approximations for heterogeneous materials. Under certain conditions, these composites can exhibit a bistable regime that the present theory properly describes in wide ranges of the concentration, shape, wavelength, dielectric contants and intrinsic non-linear optical susceptibility of the nonlinear component as well as in terms of the intensity of the external electric field. The present approach has been used to calculate the nonlinear optical response of Cu-Al2O3 nanocomposites., The authors would like to acknowledge clarifying discussions with Dr C. N. Afonso. We also thank Dr C. Flytzanis, Dr R. Serna, Dr P. Garcı´a and Dr J. Solis for a number of helpful comments. This work was funded by the Comisio´n Interministerial de Ciencia y Tecnologia (Spain), under project TIC99-0866 and by the Ministerio de Ciencia y Tecnologia (Spain) under a Ramo´n y Cajal project. F.J.G.V. acknowledges a Ramo´n y Cajal contract from the Ministerio de Ciencia y Tecnologia (Spain).

Nature Geoscience http://dx.doi.10.1038/ngeo1314 (2011); published online 13 November 2011; corrected online 29 November 2011 This manuscript was originally incorrectly published as an Article. It has now been changed to the correct category of a Letter in all versions.

[Full-text paper not available yet], The dynamics and the reactivity of the plasma produced during pulsed laser ablation of LiNbO3 have been investigated. Optical emission spectroscopy combined with time-gated imaging with high spatial resolution is applied to the study of the factors that influence the plasma expansion process, the dynamics of the ejected species the influence of a background atmosphere (O2 and Ar) and the reactivity of the expanding plasma. Direct evidence for O2 dissociation occurring during expansion is presented and the temporal evolution of the spatial distribution of the dissociated O2 is studied in detail. The influence of dissociation and velocities of the ablated species on the quality of thin films grown by pulsed laser deposition are discussed., This work was partially funded by CICYT (Spain), under Project No. TIC 2002-03235 and by European Union under Project No. HPRN-CT-2002-00328.

We have calculated the concentration of ions in the plasma produced upon ablation of LiNbO3 with a low fluence ArF excimer laser in vacuum and different gas environments (Ar and O2). The model shows that Li and Nb ions (with the amount of Li ions being greater than that of Nb ions) are the most abundant in the plasma with their concentrations being always above their corresponding neutral densities. In addition, we show that the concentration of excited Nb ions is relatively important while no excited Li ions are predicted. We found that the concentration of both Li and Nb ions in O2 is slightly higher than in Ar and vacuum. Moreover, the calculated spatial evolution of the ionic species suggests that a significant fraction of the predicted ion concentration is not produced by electron–atom ionization events within the plasma; on the contrary, they might have been produced in the LiNbO3 crystal through a nonthermal mechanism and then ejected from the target after the laser pulse.

Thedatathatsupportthefindingsof the paper "Blue Flashes as Counterparts to Narrow Bipolar Events: The Optical Signal of Shallow In-Cloud Discharges". Data Description: Cloudscat_data: The modeling data based on Cloudscat model for eight Blue LUminous Events (BLUEs). MMIA_data: The photometer signals and its images for eight Blue LUminous Events (BLUEs) measured from the Modular Multispectral Imaging Array (MMIA) of ASIM. New_eq2_data: The modeling data based on the proposed eqation(2) for eight Blue LUminous Events (BLUEs).

The data that support the findings of the paper "Blue Flashes as Counterparts to Narrow Bipolar Events: The Optical Signal of Shallow In-Cloud Discharges". Data Description: Cloudscat_data: The modeling data based on Cloudscat model for eight Blue LUminous Events (BLUEs). MMIA_data: The photometer signals and its images for eight Blue LUminous Events (BLUEs) measured from the Modular Multispectral Imaging Array (MMIA) of ASIM. New_eq2_data: The modeling data based on the proposed eqation(2) for eight Blue LUminous Events (BLUEs).