Molecular Oxygen Ions Research Articles

Effect of the NO concentration on the ratio I₅₅₇.₇/I₄₂₇.₈ in auroras

We have examined the effect of the nitrogen oxide concentration on the ratio between λ557.7 nm and λ427.8 nm emission intensities in auroras caused by precipitating electron fluxes, using the numerical simulation method. The ratio I₅₅₇.₇/I₄₂₇.₈ has been shown to strongly depend on the NO concentration: the ratio decreases from 7 to 2 with increasing NO maximum concentration at the height profile from 10⁷ to 3·10⁹. This fact is in satisfactory agreement with experimental data.The effect of nitric oxide on the ratio has been demonstrated to occur through the excitation channel of the emission λ557.7 nm, namely, the dissociative recombination of the molecular oxygen ion O⁺₂+eₜₕ due to the ion deactivation by collision reaction with nitric oxide O⁺₂+NO.

Влияние концентрации NO на отношение I₅₅₇.₇/I₄₂₇.₈ в полярных сияниях

We have examined the effect of the nitrogen oxide concentration on the ratio between λ557.7 nm and λ427.8 nm emission intensities in auroras caused by precipitating electron fluxes, using the numerical simulation method. The ratio I₅₅₇.₇/I₄₂₇.₈ has been shown to strongly depend on the NO concentration: the ratio decreases from 7 to 2 with increasing NO maximum concentration at the height profile from 10⁷ to 3·10⁹. This fact is in satisfactory agreement with experimental data.The effect of nitric oxide on the ratio has been demonstrated to occur through the excitation channel of the emission λ557.7 nm, namely, the dissociative recombination of the molecular oxygen ion O⁺₂+eₜₕ due to the ion deactivation by collision reaction with nitric oxide O⁺₂+NO.

Prospect for precision quantum logic spectroscopy of vibrational overtone transitions in molecular oxygen ions

Precision spectroscopy has been the driving force for progress of our physical understanding and still is a promising tool for the investigation of new physics. Molecules offer transitions which allow tests that are not possible in atomic systems. However, usually precision spectroscopy of molecules is challenging due to the lack of cycling transitions for state preparation and state detection. For molecular ions, this obstacle can be overcome by quantum logic spectroscopy, where dissipation for state preparation and detection is provided by a co-trapped atomic ion exploiting the shared eigenstates of motion. Here, we propose a full quantum logic spectroscopy scheme for molecular oxygen ions and theoretically investigate the feasibility of quantum logic-assisted state detection and preparation. Furthermore, we provide coupling rates for a direct single-photon quadrupole excitation of a vibrational overtone transition that can serve as a sensitive reference for tests of a possible variation of the proton-to-electron mass ratio.

Distribution of O<sup>+</sup> and ${\text{O}}_{\text{2}}^{\text{+}}$ fluxes and their escape rates in the near-Mars magnetotail: A survey of MAVEN observations

Tailward ion outflows in the Martian-induced magnetotail are known to be one of the major channels for Martian atmospheric escape. On the basis of nearly 6.5 years of observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we investigate the statistical distribution of tailward and Marsward fluxes of heavy ions (i.e., O⁺ and <inline-formula><tex-math id="Z-20220914082156">\begin{document}${\rm{O}}_2^+ $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="RA335-duhengle-F_Z-20220914082156.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="RA335-duhengle-F_Z-20220914082156.png"/></alternatives></inline-formula>) in the near-Mars magnetotail and explore their characteristic responses to the corotating interaction region (CIR), solar wind dynamic pressure, and local magnetic field intensity. Our results show that the tailward fluxes of oxygen ions and molecular oxygen ions in the magnetotail are significantly greater than their Marsward fluxes and that the tailward flux of molecular oxygen ions is generally larger than that of oxygen ions. Furthermore, the tailward ion flux distribution exhibits dependence on the CIR, solar wind dynamic pressure, and local magnetic field strength in a manner stronger than the Marsward ion flux distribution. According to the distribution of tailward ion fluxes, we calculate the corresponding escape rates of heavy ions and show that when the CIR occurs, the total escape rates of oxygen ions and molecular oxygen ions increase by a factor of ~2 and ~1.2, respectively. We also find that the escape rates of heavy ions increase with the enhancement of solar wind dynamic pressure, whereas the overall effect of the local magnetic field is relatively weak. Our study has important implications for improved understanding of the underlying mechanisms responsible for the Martian atmospheric escape and the evolution of the Martian atmospheric climate.

Interaction of molecular oxygen ions with copper surface: features of the energy spectra of sputtered and backscattered ions

An experimental study on the energy spectra of ions emitted from the surface of a polycrystalline Cu target under the bombardment by 2 keV O2+ molecular ions was carried out. Sputtered atomic ions Cu+ and O+ were prevailed among the positively charged secondary ions, and among the negative ions, in addition to sputtered ions Cu-, CuO2-, O-, and O2-, intense elastically and inelastically backscattered O-, and O2+ ions were revealed. Keywords: energy spectra, ion sputtering, backscattered ions, charge exchange.

RF and Microwave Ion Sources Study at Institute of Modern Physics

Intense ion beam production is of high importance for various versatile applications from accelerator injectors to secondary ion mass spectrometry (SIMS). For these purposes, different types of ion beams are needed and, accordingly, the optimum plasma to produce the desired ion beams. RF-type plasma features a simple structure, high plasma density and low plasma temperature, which is essential for negative ion beam production. A very compact RF-type ion source using a planar coil antenna has been developed at IMP for negative molecular oxygen ion beam production. In terms of high-intensity positive ion beam production, 2.45 GHz microwave power-excited plasma has been widely used. At IMP, we developed a 2.45 GHz plasma source with both ridged waveguide and coaxial antenna coupling schemes, tested successfully with intense beam production. Thanks to the plasma built with an external planar coil antenna, high O2− production efficiency has been achieved, i.e., up to 43%. With 2.45 GHz microwave plasma, the ridged waveguide can support a higher power coupling of high efficiency that leads to the production of intense hydrogen beams up to 90 emA, whereas the coaxial antenna is less efficient in power coupling to plasma but can lead to attractive ion source compactness, with a reasonable beam extraction of several emA.

Investigation of the process of reactive ion-beam sputtering of gallium arsenide using optical emission spectroscopy

The aim of this work was to study the process of reactive ion-beam sputtering of gallium arsenide using optical emission analysis of plasma in the target region to determine the optimal conditions for the formation of intrinsic GaAs oxides. The ion source was a plasmatron based on an anode layer accelerator (UAS), which generated a stream of accelerated argon and oxygen ions with an energy of 400–1200 eV. The target was made from tellurium doped gallium arsenide. Intense GaI lines (2874.2 Å, 2943.6 Å, 4033.0 Å and 4172.1 Å), atomic argon ArI, argon ions, and also FeI lines were detected in the spectrum upon sputtering of GaAs by Ar+ ions. The appearance of iron lines can be explained by the sputtering of the pole tips of the magnetic system of the ion source. An increase in the accelerating voltage from 1 to 3 kV leads to an increase in the intensity of the peaks of atomic gallium GaI (4172.1 Å) by 2.38 times, the GaI line (4033.0 Å) by 3.25 times, the GaI line (2943.6 Å) 3.4 times, GaI lines (2874.2 Å) 5 times. It was found that an increase in the partial pressure of oxygen leads to a sharp decrease in the peaks of GaI (4033.0 Å) and GaI (4172.1 Å) due to the chemical interaction of gallium and oxygen. Sputtering in pure oxygen reduces the intensity of these peaks by 8 and 5 times, respectively. The intensities of the peaks of atomic gallium GaI (2874.2 Å) and GaI (2943.6 Å) decreased in 2 and 1.78 times, respectively. In the presence of a positive potential on the target, the intensity of all lines of atomic gallium monotonically decreases with increasing potential. In the emission spectrum, lines of atomic oxygen OI (7774.2 Å) and molecular positive ions O+2 (6418.7 Å, 6026.4 Å, 5631.9 Å and 5295.7 Å) were detected. In the presence of a positive potential on the target, a monotonic decrease in the intensity of the above oxygen lines was observed. This indicates an intensification of chemical interaction of oxygen with target elements and, accordingly, a decrease in the free active oxygen particles.

Rapid Landau Heating of Martian Topside Ionospheric Electrons by Large‐Amplitude Magnetosonic Waves

AbstractAtmospheric escape is a fundamental process in the long‐term habitability evolution of terrestrial planets. Recent observations on Mars have found the concurrence of the severe ionospheric erosion and the large‐amplitude, quasi‐perpendicular magnetosonic waves. However, whether and then how these magnetosonic waves had contributed to the ionospheric erosion remains unclear. Here we propose a new candidate mechanism, electron Landau heating by magnetosonic waves, for the Martian ionospheric erosion. In contrast to the cyclotron resonance with oxygen atomic and molecular ions above the escape energies, the magnetosonic waves Landau‐resonate with the thermal electrons at energy channels of the order of 0.01–0.1 eV. Through the Landau resonance over tens of minutes, the large‐amplitude (12 nT) magnetosonic waves can heat the topside ionospheric electrons to ∼2 times the normal temperature. The topside ionospheric electron heating could result in the enhancement of the ambipolar electric potential and eventually facilitate the escape of ionospheric plasma.

Investigation of structural and optical properties of zirconia dioxide nanoparticles by radiation and thermal methods

The X-ray diffraction (XRD) spectrum of the nano-ZrO2compound was drawn, the crystal structure was determined at room temperature and under normal conditions. Radiation-thermal decomposition of water on nanosized ZrO2in the temperature range of [Formula: see text]–673 K has been studied by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. It has been shown that nanosized zirconium dioxide adsorbs water via the molecular and dissociative mechanisms. Intermediate products of the radiation-induced heterogeneous decomposition of water, namely, the molecular oxygen and hydrogen peroxide radical ions, zirconium hydride, and hydroxyl radicals have been detected. A comparative analysis of changes in the absorption bands (ABs) of molecular water and surface hydroxyl groups with temperature has been conducted, and the stimulating role of radiation in the radiation-thermal process of water decomposition has been revealed. With the participation of nano-ZrO2during the radiation-heterogeneous decomposition of water to reveal the role of unbalanced cargo carriers that play the role of energy carriers under the influence of gamma-quantities in nano-ZrO2and nano-[Formula: see text] systems paramagnetic centers, their origin and acquisition kinetics learned by the EPR method.

Phobos Surface Sputtering as Inferred From MAVEN Ion Observations

AbstractPhobos is bombarded by both protons and alpha particles from the solar wind and by Martian atomic and molecular oxygen ions. A numerical model of the distribution of planetary ions has previously proposed that these ions may dominate solar wind ions in sputtering the surface of Phobos when the moon is located downstream of Mars. This conclusion suggests a unique link between planetary atmospheric escape at Mars and the surface processing of its moon yet, remains to be confirmed with in situ ion measurements. In this article, a 4‐year‐long average of the ion environment that Phobos is exposed to is constructed from in situ ion observations conducted by the Mars Atmosphere and Volatile Evolution (MAVEN) mission. In turn, the flux of material sputtered from the surface of Phobos by this environment is computed. We confirm that planetary atomic oxygen ions dominate over solar wind ions in sputtering the surface of Phobos downstream of Mars during 20% of the moon's orbit. We also reveal that molecular oxygen ions sputter the surface of Phobos as much as or more than atomic oxygen ions in the Martian magnetotail. In addition to the long‐term average picture, the time variation of Phobos surface sputtered fluxes is investigated during the series of solar wind events that hit the Martian system in March 2015. We find that the flux of material liberated from Phobos' surface increased by a factor of 50 during this period.

Efficient degradation of chloramphenicol by zero-valent iron microspheres and new insights in mechanisms

Chloramphenicol (CAP) has been extensively used in the broad-spectrum antibiotic therapy so that its excessive emission has brought about serious contamination in aquatic environments. It is of great concern to find an efficient removal method and understand the transformation pathways. In this study, we developed the zero-valence iron based catalytic technique by synthesizing regular zero-valence iron microspheres (ZVI MPs), which could completely remove the CAP pollutant (20 mg L−1) within 15 min. When the CAP concentration increased to 50 mg L−1, the removal efficiency achieved to 95.5% after 15 min of reaction. The chemical evolutions of iron species on the catalyst surface and changes in components of the solution demonstrated the activation of molecular oxygen and hydrogen ion by ZVI MPs. The generation of OH and H radicals as well as their contributions to CAP degradation were confirmed by electron spin resonance and trapping experiments during the reaction. Further experiments including the intermediates identification revealed a possible degradation pathway. To the best of our knowledge, the mechanism of CAP degradation by ZVI was proposed for the first time involving both reductive and oxidative transformations with a prerequisite of efficient reductive dechlorination. The complete dechlorination of CAP molecules was confirmed by the detection of inorganic Cl– concentration (0.124 mmol L−1 after reaction), which generally lowered the toxicity of the products. These findings not only provided an efficient and economic zero-valent iron technique for eliminating the antibiotic pollutants in water, but also made important contributions to better understand the removal mechanism.

Determination of the Signal Fluctuation Threshold of the Temperature‐Ion Composition Ambiguity Problem Using Monte Carlo Simulations

AbstractUnambiguously estimating the plasma parameters of the ionosphere at altitudes between 130 and 300 km presents a problem for the incoherent scatter radar (ISR). At these ranges, ISR is unable to distinguish between different mixtures of molecular ions (NO+ and O2+) and atomic oxygen ions (O+). Common solutions to this problem are either to employ empirical or theoretical models of the ionosphere or to add a priori known plasma parameter information obtained from the plasma line of the ISR spectrum. Studies have demonstrated that plasma parameters can be unambiguously estimated in almost noiseless scenarios, not commonly feasible during routine monitoring. In this study, we define a theoretical framework to quantify the ambiguity problem and determine the maximum signal fluctuation levels of the ISR signal to unambiguously estimate plasma parameters. We conduct Monte Carlo simulations for different plasma parameters to evaluate the estimation performance of the most commonly used nonlinear least squares optimization algorithm. Results are shown as probability curves of valid convergence and correct estimation. We use simulations to quantify the estimation error when using ionospheric models as initial conditions of the optimization algorithm. We also determine the contribution to the estimation process of different combinations of parameters known from the plasma line, the particular contribution of each plasma parameter, and the effect of increasing the level of uncertainty of the parameters known a priori. Results suggest that knowing a priori both electron density and electron temperature parameters allows an unambiguous estimation even at high fluctuation levels.

State-selective dissociation dynamics of an oxygen molecular ion studied with single-harmonic pump and infrared-probe pulses

Laser-induced dissociation of a photoionized oxygen molecule is studied employing an extreme-ultraviolet-pump--near-infrared-probe (EUV-NIR pump-probe) technique. A combination of a narrow-band 11th harmonic pump centered at 17.3 eV and a moderate-intensity NIR probe restricts the dissociation dynamics to the pair of low-lying cationic states, $a{\phantom{\rule{0.16em}{0ex}}}^{4}{\mathrm{\ensuremath{\Pi}}}_{u}$ and $f{\phantom{\rule{0.16em}{0ex}}}^{4}{\mathrm{\ensuremath{\Pi}}}_{g}$. The measured kinetic energies of the ${\mathrm{O}}^{+}$ fragments reveal contributions from one-, two-, and three-photon dissociation pathways ($1\ensuremath{\omega}$, $2\ensuremath{\omega}$, and $3\ensuremath{\omega}$) involving these two states. While the yields of the two- and three-photon channels initially rise and then decrease as a function of EUV-NIR delay, the yield of the single-photon pathway rises slower but keeps increasing over the whole delay range studied. This behavior reflects the evolving probability density of the ionic nuclear wave packet at the internuclear distances, where it can undergo resonant $3\ensuremath{\omega}$ and $1\ensuremath{\omega}$ transitions from the $a{\phantom{\rule{0.16em}{0ex}}}^{4}{\mathrm{\ensuremath{\Pi}}}_{u}$ to the $f{\phantom{\rule{0.16em}{0ex}}}^{4}{\mathrm{\ensuremath{\Pi}}}_{g}$ state of ${\mathrm{O}}_{2}{}^{+}$.

Quantification of the gas phase methyl iodide using O2+ as the reagent ion in the PTR-ToF-MS technique

The charge-transfer-reaction between molecular oxygen ions (O2+) and methyl iodide (CH3I) is studied to investigate if consistent environmental quantification of the gas phase CH3I is possible without prior calibration. The neutral CH3I molecule was chosen because this compound is of atmospheric chemistry and environmental importance in the field of nuclear power plant safety and nuclear energy. Molecular oxygen was used as a reagent ion source in a commercial Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) to produce molecular oxygen ions (O2+). The use of O2+ ions allows for fast, sensitive and specific detection of gas phase CH3I via an electron exchange reaction O2+ + CH3I → CH3I+ + O2. The instrument response was linear in the 0.23–150 ppbv range and its sensitivity was humidity independent. The detection sensitivity of CH3I normalized by the O2+ count rate of 106 cps was found to be S = 22.6 ± 0.3 ncps/ppbv, independent of relative humidity. A typical O2+ primary ion signal was (2.0±0.2)×106 cps. The lowest measured CH3I concentration was 0.23 ± 0.10 ppb. Error is ±σ. The theoretical collision rate based on the dipole moment and molecular polarizability values is calculated using the Langevin collision rate (kL) approximation, the average-dipole-orientation (ADO) theory and the capture rate coefficient (kCAP) based on trajectory calculations. The experimental rate constant, kexp, for the electron transfer reaction between O2+ ions and CH3I is calculated to be 1.72±0.22×10-9 cm3s−1. Listed errors are ±σ and represent precision only. The experimentally determined value agrees very well with the theoretical collision rate values, kL=1.24×10-9 cm3s-1, kADO=1.73×10-9 cm3s−1 and kCAP=1.48×10-9 cm3s-1. The obtained results indicate that the PTR-MS technique is an excellent analytical method to quantify gas phase CH3I.

Studying Townsend and glow modes in an atmospheric-pressure DBD using mass spectrometry

Ambient molecular beam mass spectrometry has been employed to examine the effects of the mode of operation and the excitation waveform on the ionic content of a helium-based atmospheric-pressure parallel plate dielectric barrier discharge. By applying 10 kHz microsecond voltage pulses with a nanosecond rise times and 10 kHz sinusoidal voltage waveforms, distinctly different glow and Townsend modes were produced, respectively. Results showed a significant difference in the dominant ion species between the two modes. In the Townsend mode, molecular oxygen ions, atomic oxygen anions and nitric oxide anions are the most abundant species, however, in the glow mode water clusters ions and hydrated nitric oxygen anions dominate. Several hypotheses are put forward to explain these differences, including low electron densities and energies in the Townsend mode, more efficient ionization of water molecules through penning ionization and charge exchange with other species in glow mode, and large temperature gradients due to the pulsed nature of the glow mode, leading to more favorable conditions for cluster formation.

On Electron Attachment and Detachment Processes in Dry Air at Low and Moderate Constant Electric Field

Results of theoretical research on ionization of dry air at different low and moderate values of constant electric field are described. Ionization processes at subthreshold, near-threshold, and suprathreshold values of electric field have been considered. Special attention to the processes of electron attachment to oxygen molecules and electron detachment from negative ions has been paid. New data on the detachment of electrons from oxygen molecular negative ions are taken into account. Plasma ionization during thermal instability has been considered.

Processes of electron attachment and detachment in near breakdown conditions in air plasma

Results of theoretical research on ionization of dry air at different low and moderate values of constant electric field are described. Special attention to the processes of electron attachment to oxygen molecules and electron detachment from negative ions has been paid. New data on the detachment of electrons from oxygen molecular negative ions are taken into account.

TEMPO-Substituted Ionic Liquids As Redox Mediators for High Performance Lithium-Oxygen Batteries

The performance of lithium-oxygen (Li-O2) batteries can be improved using redox mediators (RMs) to promote the decomposition of the insoluble, electronically insulating discharge product Li2O2 during the charging process. Homogenous RMs are expected to have a better performance in Li-O2 batteries than heterogeneous catalysts due to a larger contact area.1 Several redox mediators have been tested, including TEMPO and its derivatives.2 However, the use of Li-O2 batteries in many applications such as electric vehicles is still restricted due to electrolyte decomposition, flammability and volatility. In order to overcome these issues, ionic liquids have been successfully used as solvents for Li-O2 batteries.3, 4 In this project, we present TEMPO-substituted imidazolium ionic liquids that can perform the dual roles of solvent and redox mediator for Li-O2batteries (Figure 1). Figure 1. Structure and cyclic voltammograms of TEMPO-substituted imidazolium ionic liquids.Ionic liquids were prepared using modified literature procedures.5-7 Cyclic voltammetry of the ionic liquids in dimethylacetamide with 0.1 M lithium bis(trifluoromethane)sulfonimide was performed using a CHI660D electrochemical workstation in combination with a conventional three-electrode cell. Figure 1 shows cyclic voltammograms for compounds with 4, 5, and 8 carbon atoms in the chains linking the TEMPO and imidazolium moieties. The ionic liquids undergo a reversible electrochemical oxidation reaction at ~0.5 V vs Ag/AgCl (~3.8 V vs Li/Li+) which means that they should be capable of oxidizing the discharge product Li2O2 upon charging to give molecular oxygen and lithium ions. The facilitation of decomposition of Li2O2 can substantially reduce the charge overpotential, thus improving the energy efficiency of Li-O2batteries. References Feng, N.; He, P.; Zhou, H. (2016) Critical Challenges in Rechargeable Aprotic Li-O2 Batteries. Advanced Energy Materials 6:1502303-152326.Bergner, B. J., Hofmann, C., Schürmann, A., Schröder, D., Peppler, K., Schreiner, P. R., Janek, J. (2015) Understanding the fundamentals of redox mediators in Li–O2 batteries: a case study on nitroxides. Physical Chemistry Chemical Physics 17:31769-31779.Zhang, T., Zhou, H. (2012) From Li-O2 to Li-Air Batteries: Carbon Nanotubes/Ionic Liquid Gels with a Tricontinuous Passage of Electrons, Ions and Oxygen. Angewante Chemie, International Edition 51:11062−11067.Zhang, T., Wen, Z.-Y. (2017) A High-Rate Ionic Liquid Lithium-O2 Battery with LiOH Product. The Journal of Physical Chemistry C, doi: 10.1021/acs.jpcc.7b00336.Qian, W., Jin, E., Bao, W., Zhang, Y. (2006) Clean and selective oxidation of alcohols catalyzed by ion-supported TEMPO in water. Tetrahedron 62:556-562.Zheng, Z., Wang, J., Chen, H., Feng, L., Jing, R., Lu, M., Hu, B., Ji, J. (2014) Magnetic Superhydrophobic Polymer Nanosphere Cage as a Framework for Miceller Catalysis in Biphasic Media. ChemCatChem 6:1626-1634.Bonhôte, P., Dias, A.-P., Papageorgiou, N., Kalyanasundaram, K., Grätzel, M. (1996) Hydrophobic, Highly Conductive Ambient-Temperature Molten Salts. Inorganic Chemistry 35:1168-1178. Figure 1

Sensing Mechanism of SnO&lt;sub&gt;2&lt;/sub&gt; (110) Surface to NO&lt;sub&gt;2&lt;/sub&gt;: Density Functional Theory Calculations

It is necessary to develop NO2 gas sensors as NO2 is a pollutant. While, different from the reducing gases, oxidizing gas NO2 will put up a complicated sensing process. Density functional theory (DFT) calculations are necessary to be performed to understand NO2-sensing mechanisms at the atomic level. In this study we introduce NO2 to SnO2 (110) surface with oxygen species pre-adsorbed. The results show that NO2 sensing mechanism of SnO2 surface strongly depends on the concentration of oxygen in the ambient atmosphere (usually, no effects of temperature and pressure are considered). The direct interactions between NO2 molecule and SnO2 sub-reduced surface (with two rows of fold-coordinated bridging oxygens removed) for very low oxygen concentrations show that, NO2 gas molecules interact directly with Sn instead of reacting with oxygen species, resulting in an increase in resistance of SnO2. We investigate gas-sensing processes of interaction between NO2 molecule and SnO2 surface with pre-adsorbed oxygen species for the case of considerable high oxygen concentrations. Adsorbed molecular oxygen ions compete with adsorbing NO2 molecules for available surface sites and electrons from the SnO2. As the availability of oxygen ions on the SnO2 surface increasing, the interaction between NO2 and adsorbed oxygen species give rise to a reducing interaction, which brings a decrease in resistance of SnO2.

Highly charged tungsten ions generated by nanosecond pulsed laser and influence of magnetic field on ion charge state

Ions emitted from the laser generated tungsten plume were investigated with the help of ion collector (IC) and electrostatic ion energy analyzer (IEA) operating in time-of-flight configuration. Plume was generated by irradiating a plane W target with 6ns pulsed Nd:YAG (λ=1064nm) laser. Laser fluence at the target was varied in the range of 3.0–19.4J/cm2. IC measurements showed that the amplitude of tungsten ions pulse increases with the laser fluence. IEA spectra indicate that the number of available Wn+ ions charge states increases from 1 to 6 when laser fluence at the target was varied in the range of 3.0–19.4J/cm2. With the application of 0.23 T axial magnetic field at the target surface, the number of available Wn+ ions charge states increases from 1 to 10 in the similar range of the laser fluence. In addition, molecular oxygen ions O2n+ were also observed when magnetic field is applied at higher values of the laser fluence. The ion charge state enhancement is presumably due to the magnetic trapping of electrons in front of the target surface, which intensifies electron impact ionization process.