Balmer Series Lines Research Articles

On the determination of plasma electron number density from Stark broadened hydrogen Balmer series lines in Laser-Induced Breakdown Spectroscopy experiments

In this work, different theories for the determination of the electron density in Laser-Induced Breakdown Spectroscopy (LIBS) utilizing the emission lines belonging to the hydrogen Balmer series have been investigated. The plasmas were generated by a Nd:Yag laser (1064nm) pulsed irradiation of pure hydrogen gas at a pressure of 2·104Pa. Hα, Ηβ, Ηγ, Ηδ, and Hε Balmer lines were recorded at different delay times after the laser pulse. The plasma electron density was evaluated through the measurement of the Stark broadenings and the experimental results were compared with the predictions of three theories (the Standard Theory as developed by Kepple and Griem, the Advanced Generalized Theory by Oks et al., and the method discussed by Gigosos et al.) that are commonly employed for plasma diagnostics and that describe LIBS plasmas at different levels of approximations. A simple formula for pure hydrogen plasma in thermal equilibrium was also proposed to infer plasma electron density using the Hα line. The results obtained showed that at high hydrogen concentration, the Hα line is affected by considerable self-absorption. In this case, it is preferable to use the Hβ line for a reliable calculation of the electron density.

The sample of FBS cataclysmic variables

The First Byurakan Survey (FBS) was conducted by Markarian et al. (1989) to reveal UV-excess galaxies. However, many other interesting objects were possible to detect based on its low-dispersion spectra, and the Second part of the FBS (Mickaelian 2008) was carried out later to reveal UV-excess stellar (point-like) objects, such as white dwarfs (WD), hot subdwarfs, cataclysmic variables (CV), HBB stars, as well as QSOs and Seyfert galaxies. In addition, the FBS plates were digitized (DFBS, Digitized First Byurakan Survey; Mickaelian et al. 2007) and the extraction and reduction of spectra allowed selection of objects with higher confidence and to fainter magnitudes.Spectroscopic observations have been carried out with three telescopes (Byurakan Astrophysical Observatory BAO-2.6m, Russian Special Astrophysical Observatory SAO-6m and Observatoire de Haute Provence OHP-1.93m) (Sinamyan & Mickaelian 2009) for classification of objects. The spectral features of CVs are narrow emission lines (Balmer series, HeI and HeII lines and Bowen band at 4640A) (Fig. 1). In addition, we use the NSVS database (Wozniak et al. 2004) for revealing variability and our method of comparison of POSS1 and POSS2 epoch photometric data (Mickaelian et al. 2011) based on accurate calculations of weighted average POSS1 and POSS2 magnitudes. 27 objects are present in the NSVS and light curves are available (Fig 2.). X-ray data may serve as an additional criterion to detect CVs among the FBS blue stellar objects (Voges et al. 1999; 2000).The subsample of FBS WDs has already been published (Sinamyan & Mickaelian 2011), where some CVs are also present. The subsample of FBS CVs consists of 38 objects, including the following types: dwarf novae (DN; UG and SU subtypes; 7 objects), nova-like variables (NL; SH, AC, VY subtypes; 11 objects), as well as there is a DQ Her type object (FBS 1140+719), a Helium CV (HeCV; FBS 1232+379), and a Low-mass X-ray Binary (LMXB; FBS 1656+354). Other objects do not have accurate classification because of the lack of photometric data. The Periods are in the range of 0.012 to 0.343 days.To make a complete study of these objects possible, multiwavelength (MW) data were retrieved for these 38 objects, including X-ray (ROSAT BSC and FSC), UV (GALEX), optical (APM, MAPS, USNO-B1.0, GSC 2.3.2, SDSS), and IR (2MASS, WISE, IRAS, AKARI) and MW SEDs were built. For CVs, MW SEDs have some disadvantage as their variability does not allow to have their accurate energy distribution. Diagrams with relations between MW data-points and some other physical parameters were also built.

Two-dimensional visualization of excitation temperature and chemical species in divertor plasmas: Trace CD molecules by chemical sputtering of fusion plasma reactor wall

The divertor region is among the most important section of nuclear fusion reactors. In order to investigate the behavior of deuterium in divertor plasmas, emission profiles of the Balmer series lines of deuterium atoms, molecular bands of D2 and CD intensities have been two-dimensionally visualized with a CCD camera fitted with a bandpass filter, using a test system, the Nagoya Divertor Simulator II (NAGDIS-II). It has been clarified that profiles of emission from deuterium atoms and excitation temperature varied significantly with changes of the discharge current. From profiles of the ratio of the atomic emission intensity to the deuterium molecular emission, the increase in the dissociation fraction of deuterium molecule with the increase of the discharge current has been confirmed. Two dimensional visualization of the divertor plasma is a promising method for studies in nuclear fusion science.

Plasma-chemical polymerization in CH4-based mixtures containing various amounts of rare gases

For constant-current glow discharge in Ar + Ne + CH4 mixtures in a pressure range of 13–250 Pa and a discharge current range of 5–100 mA, the following characteristics were determined: gas temperature; longitudinal electric field intensity; radiation line intensities of Ne (3p → 3s) and Ar (4p → 4s) transitions; intensities of Hα, Hβ, and Hγ lines of Balmer series; concentrations of Ne, Ar, and H atoms in metastable and resonance states; concentration of atomic hydrogen; and growth rate of polymer films. The composition of the polymer films was analyzed with the use of infrared spectroscopy. Mathematical modeling of discharges under the selected conditions was carried out. The results of calculations were compared to the experimental data. The mechanism of processes that proceed in the glow discharge plasma is shown to depend strongly on the Ne-to-Ar concentration ratio, which results in the qualitative difference between the compositions of films that were grown at the same pressure and discharge current, as well as in the difference between the growth rates of the films.

Modelling of passive spectroscopy in the ITER divertor: the first hydrogen Balmer lines

The first lines of the hydrogen Balmer series are investigated in ITER divertor conditions using a line shape code and a plasma edge transport code. It is shown that most of the emissivity originates from a localized, cold and dense region close to the divertor target plates, where the plasma is in the recombining regime. We simulate the signal obtained by pointing a spectrometer at this zone. The physical processes which contribute to the spectral line formation are examined, with a special emphasis on the Stark effect, photon absorption and stimulated emission. It is shown that, even though the Stark effect is significant, local information on the Doppler atomic temperature can be obtained from a fitting analysis of the Dα spectral line shape.

Selective atomic hydrogen heating in plasmas: Implications for quantum theory

A new model of quantum mechanics, Classical Quantum Mechanics, is based on the (nearly heretical) postulate that electrons are physical objects that obey classical physical laws. Indeed, ionization energies, excitation energies, etc. are computed based on picturing electrons as ‘bubbles’ of charge that symmetrically surround a nucleus. Hence, for example, simple algebraic expressions based on Newtonian force balances are used to predict ionization energies and stable excitation states with remarkable precision. One of the most startling predictions of the model is that there are stable ‘sizes’ of the hydrogen atom electron (bubble diameter) that are smaller (‘hydrinos') than that calculated for the ‘ground state’. Experimental evidence in support of this novel physical/classical version of quantum is alleged to be found in the existence of super-heated hydrogen atoms reported by many teams in a variety of plasmas. It is postulated that the energy required for creating super-heated H atoms comes from the shrinkage of ground state H atoms to form hydrinos. This claim is discussed with reference to a brief review of the published studies of selective Balmer series line broadening in pure H 2 and mixed gas plasmas, and astrophysical data.

Growth and properties of the ion beam deposited SiO x containing DLC films

In the present study SiO x containing diamond-like carbon (DLC) films were synthesized by the closed drift ion source from hexamethyldisiloxane vapor. Kinetics of the growth of DLC films was investigated using optical emission spectroscopy (OES). Structure, chemical composition, electrical and optical properties of the synthesized films were studied. The effects of ion beam energy were investigated. The main atomic hydrogen Balmer series lines and the intense broad CH group related peak were detected in the OES spectra registered in-situ during SiO x containing diamond-like carbon film synthesis. The intensity ratio of H-β/CH peaks increased with the increase of applied ion beam energy. It was explained by activation of the dissociation of the hexamethyldisiloxane molecules. Changes of the structure of the diamond-like carbon films were observed for the films deposited under intense dissociation conditions.

Evidence of catalytic production of hot atomic hydrogen in RF generated hydrogen/helium plasmas

A study of the line shapes of hydrogen Balmer series lines in RF generated low pressure He/H 2 plasmas produced results suggesting a catalytic process between helium and hydrogen species results in the generation of ‘hot’ (ca. 28 eV) atomic hydrogen. Even far from the electrodes ‘hot’ atomic hydrogen was predominant in He/H 2 plasmas. Line shapes, relative line areas of cold and hot atomic hydrogen (hot/cold > 2.5), were very similar for areas between the electrodes and far from the electrodes for these plasmas. In contrast, in Xe/H 2 only ‘warm’ (<5 eV) hydrogen (warm/cold < 1.0) was found between the electrodes, and only cold hydrogen away from the electrodes. Earlier postulates that preferential hydrogen line broadening in plasmas results from the acceleration of ionic hydrogen in the vicinity of electrodes, and the special charge exchange characteristics of Ar/H 2+ are clearly belied by the present results that show atomic hydrogen line shape are similar for He/H 2 plasmas throughout the relatively large cylindrical (14 cm ID × 36 cm length) cavity.

Evidence for a Companion to BM Gem, a Silicate Carbon Star

Balmer and Paschen continuum emission, as well as Balmer series lines of P Cygni-type profile from Hγ through H23, are revealed in the violet spectra of BM Gem, a carbon star associated with an oxygen-rich circumstellar shell (silicate carbon star). The blueshifted absorption in the Balmer lines indicates the presence of an outflow, the line-of-sight velocity of which is at least 400 km s−1. The Balmer lines show a significant change in profile over a period of 75 days. We argue that the observed unusual features in BM Gem are strong evidence for the presence of a companion, which should form an accretion disk that gives rise to both an ionized gas region and a high-velocity variable outflow. The estimated luminosity of ~0.2 (0.03-0.6) L☉ for the ionized gas can be maintained by a mass accretion rate for a dwarf companion of ~10−8 M☉ yr−1, while ~10−10 M☉ yr−1 is sufficient for accretion to a white dwarf companion. These accretion rates are feasible for some detached binary configurations on the basis of the Bondi-Hoyle-type accretion process. Therefore, we conclude that the carbon star BM Gem is in a detached binary system with a companion of low mass and low luminosity. However, we are unable to determine whether this companion object is a dwarf or a white dwarf, although the gas outflow velocity of 400 km s−1, as well as the nondetection in the X-ray survey, favor its identity as a dwarf star. The upper limits for binary separation are 210 and 930 AU for a dwarf and a white dwarf, respectively, in the case of circular orbit. We also note that the observed features of BM Gem mimic those of Mira (o Cet), which may suggest actual similarities in their binary configurations and circumstellar structures.

Ionization Balance in the Rotating Radiation Belt Accompanying Complete Divertor Detachment in LHD

A spectroscopic measurement is performed for a plasma in a rotating radiation belt, which accompanies the complete divertor detachment recently realized in the Large Helical Device (LHD) [J. Miyazawa et al., Nucl. Fusion 46, 532 (2006)]. The population distribution over the exited levels is experimentally determined from the Balmer series line intensities and is compared with the result of the collisional-radiative model calculation to determine the electron temperature Te and density ne. No reasonable pair of Te and ne is found when either the ionizing plasma or the recombining plasma is assumed. A good fitting is obtained under an assumption of the ionization balance plasma with Te = 1.8 eV and ne = 2 × 1020 m-3. These parameters are confirmed through analysis of a high-wavelength-resolution measurement for the Balmer series lines which clearly exhibit the Stark broadening effect.

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

This is the third in a series of papers by our team on apparently anomalous Balmer series line broadening in hydrogen containing RF generated, low-pressure ( < 600 mTorr ) plasmas. In this paper the selective broadening of the atomic hydrogen lines in pure H 2 and Ar / H 2 mixtures in a large general electronics conference (GEC)-type cell (36 cm length × 14 cm ID) was mapped as a function of position, H 2 / Ar ratio, time, power, and pressure. Several observations regarding the selective line broadening were particularly notable as they are unanticipated on the basis of earlier models. First, the anomalous broadening of the Balmer lines was found to exist throughout the plasma, and not just in the region between the electrodes. Second, the broadening was consistently a complex function of the operating parameters, particularly gas composition (highest in pure H 2 ) position, power, and pressure. Clearly, not anticipated by earlier models were the findings that under some conditions the highest concentration of “hot” ( > 10 eV ) hydrogen was found at the gas entry end, and not in the high-field region between the electrodes, and that in other conditions, the hottest H was at the (exit) pump (also grounded electrode) end. Third, excitation and electron temperatures (measured optically) were less than 1 eV in all regions of the plasma not directly adjacent ( > 1 mm ) to the electrodes, providing additional evidence that the energy for broadening, contrary to standard models, is not obtained from the electric field. Fourth, in contrast to our earlier studies of hydrogen/helium and water plasmas, we found that in some conditions 98% of the atomic hydrogen was in the “hot” state throughout the GEC-type cell. Virtually every operating parameter studied impacted the character of the hot H atom population. Clearly, second and third order effects exist, indicating a need for experimental design. Some non-field mechanisms for generating hot hydrogen atoms are outlined.

Coupling and ionization effects on hydrogen spectral line shapes in dense plasmas

A study of hydrogen lines emitted in dense and low temperature plasmas is presented. Coupling and ionization effects in a transition from impact to quasi-static broadening for electrons are analyzed with the help of the Frequency Fluctuation Model (FFM). Electron broadening of Balmer series lines is studied for different densities and temperatures spanning a wide domain from impact to quasi-static limit. It is shown that electronic broadening makes a transition from impact to quasi-static limit depending on plasma conditions and principal quantum number. Even for the Balmer alpha line, at a density equals 1018 cm-3 and a temperature equals 1 eV, this transition occurs both in the wings and the core of the line.

Line shape modeling in warm and dense hydrogen plasmas

A study of hydrogen lines emitted in warm ( T e ∼ 1 eV ) and dense ( N e ≥ 10 18 cm −3 ) plasmas is presented. Under such plasma conditions, the electronic and the ionic contributions to the line width are comparable, and the general question related to a transition from impact to quasi-static broadening arises not only for the far wings but also for the core of spectral lines. The transition from impact to quasi-static broadening for electrons is analyzed by means of Frequency Fluctuation Model (FFM). In parallel, direct integration of the semi-classical evolution equation is performed using electron electric fields calculated by Molecular Dynamics (MD) simulations that permit one to correctly describe the emitter environment. New cross comparisons between benchmark MD simulations and FFM are carried out for electron broadening of the Balmer series lines, and, especially, for the H α line, for which a few experiments in the warm and dense plasma regimes are available.

Two-Dimensional Spectroscopic Measurement of Hydrogen Emission in JT-60U Divertor Plasmas

In JT-60U divertor plasmas, deuterium Balmer-series line emission has been measured with a wide-spectral-band spectrometer, which has 92 viewing chords with a ˜1cm spatial resolution. Two-dimensional spatial distribution of the Balmer line intensities has been reconstructed using a computer tomography technique (maximum entropy method). In an inner-detached and outer-attached divertor plasma, the intensity of Dβ and Dγ lines were stronger above the strike point in the inner divertor and near the strike point in the outer divertor. The ratio of the Dγ line intensity to the Dβ line intensity was 0.3 - 0.5 above the strike point in the inner divertor and 0 - 0.2 near the strike point in the outer divertor. It suggested that the line emission were attributed to the plasma recombination above the strike point in the inner divertor and the plasma ionization near the strike point in the outer divertor.

Measurements of aluminum and hydrogen microplasma

We report time-averaged and time-resolved emission spectra subsequent to laser-induced optical breakdown of aluminum in laboratory air and in hydrogen gas. The microplasma generated by nominal 10 ns IR laser radiation shows Stark-broadened and shifted atomic lines. An analysis of the H(alpha) and H(beta) Balmer series lines and selected aluminum lines allows one to determine electron number density in the range of 0.01 - 10 x 10(18) cm(-3) early in the plasma decay. Atomic and molecular features are investigated for diagnostic applications in laser material processing.

Modification of Tomography Technique for Two-Dimensional Spectroscopic Measurement in JT-60U Divertor Plasmas

Tomography techniques using the two measurement arrays were investigated. To evaluate test reconstruction methods with three combinations of calculation grid and observation view lines, a model distribution was reconstructed. The two-dimensional distribution generated on a calculation grid arranged parallel to the actual apparatus view lines was in better agreement with the model distribution than the distribution generated on a square grid. This parallel grid was applied to the reconstruction of the deuterium Balmer-series lines in the JT-60U detached divertor plasmas.

The coronal structure of Speedy Mic – II. Prominence masses and off-disc emission*

Observations of stellar prominences on young rapidly rotating stars provide unique probes of their magnetic fields out to many stellar radii. We compare two independently obtained data sets of the K3 dwarf Speedy Mic (BO Mic, HD 197890) using the Anglo-Australian Telescope (AAT) and the European Southern Observatory (ESO) Very Large Telescope (VLT). Taken more than a fortnight apart, they provide the first insight into the evolution of the prominence system on such a young rapidly rotating star. The largest prominences observed transiting the stellar disc are found at very similar rotational phases between the epochs. This suggests that the magnetic structures supporting the prominences retain their identity on a two to three week time-scale. By taking advantage of the high signal-to-noise ratio and large wavelength range of the VLT observations, we identify prominences as transient absorption features in all lines of the hydrogen Balmer series down to H10. We use the ratios of the prominence equivalent widths (EWs) in these lines to determine their column densities in the first excited state of hydrogen. We determine the optical depths, finding prominences to be rather optically thick (τ≈ 20) in the Hα line. The total hydrogen column density and thus the prominence masses are determined via observations of the Ca II H&K lines. We find typical masses for four of the largest prominences to be in the range 0.5–2.3 × 1014 kg, slightly larger than giant solar prominence masses. Rotationally modulated emission is seen outside of the Hα line. These loops of emission are shown to be caused by prominences seen off the stellar disc. We find that all of the large emission loops can be associated with prominences we see transiting the stellar disc. This, combined with the fact that many prominences appear to eclipse the off-disc emission of others, strongly suggests that the prominence system is highly flattened and likely confined to low stellar latitudes.

Plasma nitriding of austenitic stainless steel in N2 and N2–H2 dc pulsed discharge

AISI 302/304 austenitic stainless steels have been nitrided in N2 and N2–H2 glow discharge plasmas powered by a high frequency dc pulsed power supply. In a pure nitrogen plasma, no increase in surface hardness from the initial value has been observed. In a N2–H2 gas admixture, a 3–4 times increase in hardness has been found, which confirms the necessity of hydrogen gas as a powerful reagent. Grazing incidence X-ray diffraction (GIXRD) shows the presence of three phases of nitride (Fe3N, Fe4N and CrN) along with iron oxide (Fe2O3). It is found in a N2 plasma at a sample temperature of 540 °C that at 200 kHz, maximum peak intensity of iron oxide/nitride decreases. In N2–H2 plasma treated sample the nitride peak intensity increased in comparison to the intensity in sample nitrided in N2 plasma. Optical emission spectroscopy (OES) has been used to investigate the active species present during nitriding in the near-cathode region. Emission bands of neutral and ionic molecular species and ionic atomic species of nitrogen have been detected in a nitrogen plasma. In a N2–H2 gas admixture, the Hα and Hβ lines of Balmer series in addition have been observed. At 20% H2 addition in nitrogen plasma, a few vibrational state intensities of N2 and N2+ are observed to be optimized.

Density Diagnostics of the Hot Plasma in AE Aquarii withXMM‐Newton

We report on XMM-Newton observations of the magnetic CV AE Aqr. High-resolution spectroscopy of the He-like triplet of N and O with the RGS has enabled us to measure the electron number density of the plasma as ~1011 cm-3. Incorporating this with the emission measure, we estimate the geometrical scale of the plasma emitting these lines to be lp (2-3) × 1010 cm. Since the density and the scale are both incompatible with the standard postshock accretion column of an mCV, the plasma cannot be a product of mass accretion onto the white dwarf. The widths of the H-like Kα emission lines of N and O (=1250-1600 km s-1) are of similar magnitude to the thermal velocity dispersion of the hottest part of the plasma, where kTmax is 4.6 keV. It is known that Balmer series and UV emission lines also show a similar velocity dispersion. In addition, like these lines, the X-ray emission lines are found to show dramatic flaring activity. These facts strongly suggest that all these broad emission lines from X-ray to optical wave bands are produced in the course of adiabatic cooling of the plasma once heated up to Tmax in the deep gravitational potential of the white dwarf. This interpretation can resolve the problem of the absence of the high-velocity component in the Hα emission line spectrum by a scenario where the plasma that is expelled due to the propeller action is still too hot to emit the Hα line within a region of r < lp (roughly equal to the Roche lobe size) from the white dwarf where the high-velocity component is expected to originate.

Absolute photon cross sections for Balmer lines from proton‐SO2 collisions

Observations of atomic emissions from the Io plasma torus and previously published laboratory work suggest that proton collisions with SO2 may be a source of some of the spectral lines. We present an analysis of Balmer series lines seen in the spectra of collisions of protons with SO2 over the range of 50 to 250 keV. Absolute emission cross sections for these lines are measured to be on the order of 10−19 cm2 and are in rough agreement with a parametric model for electron capture which supports charge‐transfer ionization of the SO2 target.