Experimental Stark Widths Research Articles

Reexamining the Stark width and shift of He ii Paschen-α: Studies using laser-induced plasma, Thomson scattering, and computer simulations.

We report on experimental and theoretical studies on the Stark profile of the Heii Paschen-α line over a wide range of plasma parameters. This line was emitted from a laser-induced plasma with electron densities in the range of 8.1×10^{22}-4.46×10^{24}m^{-3} and electron temperatures of 1.2-7.6eV as independently measured using the two-color Thomson scattering method. The line shapes were calculated using a computer simulation method, treating the ions and electrons on an equal footing and taking into account the full Coulomb interaction between the hydrogenlike atomic radiator and plasma perturbers penetrating the wave-function extent of the bound electron. We found a very good agreement between the experimental and theoretical Stark widths and shifts, which on average agree within 5%. In addition, practical analytical approximations for the linewidth and line shift are provided, validated against extensive calculations in the density and temperature ranges of 10^{23}-10^{25}m^{-3} and 1-16eV, respectively.

Experimental and Semiclassical Stark Widths and Shifts for Spectral Lines of Neutral and Ionized Atoms (A Critical Review of Experimental and Semiclassical Data for the Period 2008 Through 2020)

This Review Article compares new experimental and corresponding semiclassical Stark broadened data for non-hydrogenic spectral lines of neutral atoms and positive ions. This Review covers the period 2008 until the end of 2020 and presents the continuation of previous critical reviews from 1976 (two), 1984 (two), 1990, 2002, and one from 2009. This Review reports the Stark broadening parameters of 1665 spectral lines belonging to 35 elements with 61 different atomic and ion species. The data are taken from 60 papers. Experimental data are arranged by elements and spectra, and these are reported in tables in alphabetical and numerical order, respectively. Each experimental Stark broadening parameter is followed with estimated accuracy. The experimental Stark broadening and shift data presented in the tables are compared with the corresponding semiclassical results available in the literature. In addition, for comparison experiments versus semiclassical theoretical Stark broadening parameters, a numerically improved theoretical approach developed based on Griem and co-workers’ theory is used to evaluate Stark widths and shifts of all studied lines whenever required atomic energy levels data and transition probabilities are available. At the end of the text report, for each analyzed neutral or ion species, the information about the location of the same species data in preceding reviews is given.

Experimental Stark widths of Mo I and Mo II spectral lines in visible region

In the last decade, molybdenum became a very important element for understanding the process of nucleosynthesis. An essential requirement for stellar spectral analysis is the availability of high-quality atomic data, including Stark broadening parameters. In this work we investigate Stark broadening of molybdenum spectral lines from the wavelength range 370 nm–510 nm. This is the first presentation of Stark widths for 18 Mo I and 18 Mo II spectral lines measured at an electron density of ≈ 1.5 × 1023 m−3 and electron temperature of ≈ 13000 K. Laser induced plasma with well isolated molybdenum spectral lines is employed as a radiation source. Spectra are recorded side-on; the line profiles are obtained via inverse Abel transform. Electron temperature is estimated using the Saha–Boltzmann method. To estimate electron density we applied two techniques. The first is based on the Saha–Boltzmann method for selected Mo I and Mo II spectral lines. In the second approach we rely on the measured width of the well-researched He I 388.86 nm line, as well as on the peak separation of the He I 447.15 nm line. Stark widths normalized to 1 × 1023 m−3 electron density are also given. The possible influence of isotope shift and hyperfine structure on spectral line profiles is discussed in detail. Stark shifts of investigated Mo I and Mo II spectral lines, if they exist, are below the detection limit of the experimental setup.

Stark broadening measurements of Al II, Al III and He I 388.86 nm spectral lines at high electron densities

Experimental Stark width broadening parameters (w) for 5 spectral lines of singly (Al II) and 8 spectral lines of doubly ionized aluminum atoms (Al III) are presented. The for Al III values are the first experimental data. The experiment was conducted in laser-induced plasma in helium‑hydrogen gas mixture at reduced pressure. The laterally resolved spectra are recorded side-on. The plasma parameters are inferred after applying inverse Abel transform. The electron densities ranging from (0.98–4.86)×1023 m−3 are estimated relying on broadening of hydrogen Hβ spectral line. The electron temperature in experiment was in the range 20000 K to 28000 K and it was determined applying Boltzmann and Saha-Boltzmann method. Stark broadening parameters for Al II and Al III spectral lines are compared with available experimental and theoretical results. We also present experimental Stark widths and shifts (d) for neutral helium 388.86 nm spectral line at electron densities above 1×1023 m−3, where the existing number of w and d data is limited. Some of new Al III w values are convenient for plasma diagnostics.

Experimental and theoretical studies of Stark profiles of Ar I 696.5 nm spectral line in laser-induced plasma

We report the results of the Stark profile studies of the 696.543 nm Ar I spectral line in laser-induced plasma generated by a nanosecond Nd:YAG laser radiation at 532 nm in argon at reduced pressure. Plasma diagnostics was performed with the use of the laser Thomson scattering method, free from assumptions about the plasma thermodynamic equilibrium, its composition but also independently of plasma emission spectra. The profiles were investigated in wide range of electron densities and temperatures, from 2.81 · 1022 m−3 to 5.69 · 1023 m−3 and from 10 430 K to 73 400 K, respectively. Stark profiles were calculated using a semi-classical method as well as by N-body numerical simulations assuming a plasma in local thermodynamic equilibrium. Our studies show agreement within 20% between experimental Stark widths and those calculated by the semi-classical method while much bigger discrepancies were found with computer simulated ones. Importantly, Stark profiles of the investigated spectral line, both experimentally determined and computed, are highly sensitive to electron temperature.

Net emission coefficient of complex thermal plasmas used in SWNT synthesis

The calculation of net emission coefficient NEC is done for mixtures He–Ar/N2–[C100−x−y−z,Bz,Nix/Cox,Yy] used in the synthesis of single-wall carbon nanotubes SWNTs by arc discharge technique, at pressure of 60 kPa and at temperature interval going from 1 kK to 30 kK. These mixtures contain helium–argon as a gaseous atmosphere, nitrogen–boron as a doping atoms and a carbon anode filled with yttrium–nickel/cobalt as catalysis. Different proportions of metallic catalysts are considered going from 0.01 atomic% (at%) to 5 at%. Whereas for doping atoms the concentration amounts are much higher and do not exceed 8 at% for boron and 50% for nitrogen. The results of NECs are obtained by summing over all wavelengths, the contributions of atomic and molecular continuum, results of free–free and free–bound transitions, and line and molecular bands emissions corresponding to bound–bound transitions. Doppler broadening, resonance, van der Waals, electron and ion Stark broadening are taken into account for the calculation of the lines widths. As Stark broadening is the most important broadening mechanism at intermediate and high temperature, an empirical correction factors determined for some resonance lines, are added to the semi-empirical Stark formulas for a best reproducing of the experimental Stark widths. The comparisons of the NECs of the pure plasmas of argon, helium, nitrogen and carbon to those given in literature present an acceptable agreement. For the studied mixtures containing He–Ar/N2–[C100−x−y−z,zBz, Nix/Cox,Yy], the obtained results show that the addition of boron or the nitrogen induces a few little changes in the NEC, in contrary to the metal catalysts where we noted a considerable increase in the plasma emission especially at low temperatures. The effect of the addition of yttrium in carbon anode even in a small amount (<0.1 at%) affects strongly the NEC compared to that of cobalt or nickel which have given similar results.

Experimental measurements of Stark widths for Mn I lines in long laser spark

We report the experimental Stark widths of Mn I lines belonging to multiplets z6P°→a6S and z6D°→a6D in long spark induced by laser. We have used aluminum alloy containing 80ppm of manganese as a target to avoid strong self-absorption of Mn I lines. Its absence was proved by the comparison of observed intensities with relative strengths of lines within multiplets. Electron density of plasma estimated by Mg I (5172.68Å) and Al II (2816.18Å) lines was within the range of (4–30)×1016cm−3. The shortest possible gate allowed the observation of symmetric atomic and ionic lines. The spatial profiles of plasma temperature and electron density along the axis of long spark demonstrated that both values were lower than for spherical plasma. Measured Stark widths of resonance multiplet z6P°→a6S decrease from 0.075Å for its first component to 0.055Å for the last one, while Stark widths of components of multiplet z6D°→a6D increase from 0.095Å to 0.125Å. No Stark shifting was observed for the studied multiplets.

Experimental Stark widths and shifts of Ti ii spectral lines

Experimental Stark widths and shifts of Ti ii spectral lines

Experimental Stark widths and shifts of Cr II spectral lines

This work has been supported by the project FIS2011-29521 of the Spanish Ministerio de Economia y Competitividad.

Measurement of Stark broadening parameters of Fe II and Ni II spectral lines by laser induced breakdown spectroscopy using fused glass samples

The Stark widths of 36 Fe II and 27 Ni II spectral lines are measured by laser induced breakdown spectroscopy (LIBS). The use of fused glass samples prepared by borate fusion is evaluated for Stark broadening measurements in LIBS experiments. The spectra of laser-induced plasmas generated from fused glass samples containing oxides show improved line-to-background ratios compared to those measured with alloys. The diagnostics of the fused glass laser induced plasmas shows that their characteristic parameters are not very different from those of alloy plasmas. The electron density in the experiment is in the range (0.8–10)×1017cm−3 and the temperature varies from 12000K to 17600K. These experimental Stark width data, most of which had not been measured previously, complete the data for Fe II and Ni II reported in earlier works, determined by LIBS using alloy samples.

Stark broadening measurement of Al II lines in a laser-induced plasma

Laser induced plasma was a light source for the study of Stark broadening parameters of singly charged aluminum ion lines. Plasma electron number density in the range (0.3–2.3)×1023m−3 was measured from the Stark width of the hydrogen Hα impurity line, while the electron temperature between 6500 and 17,500K was determined from relative intensities of Fe II, Mg I and Al II spectral lines using the Boltzmann plot technique. The experimental Stark widths were compared with other experiments and theories, which include semiclassical results and data evaluated from the modified semiempirical formula.

Stark width measurements of Fe II lines with wavelengths in the range 230–260 nm

The experimental Stark widths of 26 Fe II lines with wavelengths in the range 230–260 nm have been determined by laser-induced breakdown spectroscopy. These measurements complete the data reported previously for the wavelength range 260–300 nm. The laser-induced plasmas have been generated from Fe–Cu and Fe–Ni samples. The curve-of-growth methodology is used to determine the iron concentration required to avoid self-absorption. The electron density at the different instants of the plasma lifetime, determined from the Stark broadening of the Hα line, is in the range (1.6–7.4) × 1017 cm−3. The plasma temperature is in the range 12 900–15 200 K. The Stark widths obtained are compared with previous experimental and theoretical data.

Net emission coefficients of argon iron plasmas with electron Stark widths scaled to experiments

The net emission coefficient of plasmas containing argon and iron at atmospheric pressure is calculated and analysed for the case of cylindrical geometry. Its values are obtained by integrating the monochromatic net emission coefficient taking into account continuous and line radiation. The width of the spectral lines is determined by Doppler broadening, natural, resonance, van der Waals, electron and ion Stark broadening. As Stark broadening is the most important broadening mechanism in the considered pressure and temperature range, the electron Stark widths are calculated following the semi-empirical Stark broadening theory. Additionally, the electron Stark widths of Ar, Ar+, Fe and Fe+ are multiplied by scaling factors in order to reproduce experimental electron Stark widths. The scaling factor is determined for each species separately. For small plasma radii the net emission coefficient determined here shows good agreement with literature values where spherical geometry is considered while they decrease faster with increasing plasma radius. This behaviour is caused by the increase of the irradiation of the symmetry axis when cylindrical instead of spherical geometry is considered. For radii and temperatures typical of the metal filled core of arcs occurring in gas metal arc welding processes, i.e. radii between 1 and 2 × 10−3 m and temperatures between 5000 and 10 000 K, the scaling of the Stark widths increases the net emission coefficient of iron plasmas by between 2% and 23%. In this parameter range the net emission coefficient of iron plasmas for cylindrical geometry is between 30% and 37% smaller than values calculated for spherical geometry.

Measurements of Stark widths and shifts of Ne I lines using degenerate four-wave mixing and Thomson scattering methods

We report on measurements of Stark widths and shifts of four prominent Ne I lines of the 3s,3s′-3p transition arrays. The measurements were performed in an atmospheric-pressure arc discharge operated in argon–neon gas mixture. Sub-Doppler degenerate four-wave mixing technique was used to measure the line profiles, while Thomson scattering yielded the plasma parameters: electron density, n e = (0 .53–1 .33) × 10 23 m − 3 , and electron temperature, T e = 10,200–20,900 K. The measured profiles are symmetric within the uncertainty limits. The experimental Stark widths and shifts are compared with results of other experiments and theoretical calculations.

Application of a laser produced plasma: Experimental Stark widths of single ionized lead lines

The optical emission spectroscopy from laser produced plasma generated by a 10,640 Å radiation, with an irradiance of 1.4 × 10 10 W cm − 2 on several lead targets, in vacuum and in an atmosphere of argon, was recorded and analyzed between 1900 and 7000 Å. The Local Thermodynamic Equilibrium conditions and plasma homogeneity have been checked. Stark widths for 31 lines of Pb II have been measured. These lines measured in this work correspond to the transitions 7s → 6p, n( n = 8, 9, 10)s → 7p, n( n = 7, 8)p → 7s, n( n = 7, 8)p → 6p 2, n( n = 7, 8)d → 7p, n( n = 5, 6)f → 6d, n( n = 5, 6)f → 6p 2. The population level distribution and the corresponding temperatures were obtained using Boltzmann plots. The plasma electron densities were determined using well-known Stark broadening parameters of spectral lines. Special attention was dedicated to the possible self-absorption of the different transitions. Temporal evolution of the plasma parameters was studied between 0.1 and 9 μs. Stark broadening parameters of the spectral lines were measured at 2.5 μs where the electron temperature was close to 11,300 K and the electron density to 0.8 × 10 16 cm − 3 . The experimental results obtained have been compared with the experimental and theoretical values given by other authors. A systematic trend of this parameter versus temperature of 4244.9 Å Pb II line has been presented.

Experimental Stark Widths and Shifts for Spectral Lines of Neutral and Ionized Atoms (A Critical Review of Selected Data for the Period 1989 Through 2000)

A critical review of the available experimental data on Stark widths and shifts for spectral lines of nonhydrogenic neutral atoms and positive ions has been carried out. The review covers the period from 1989 through the end of 2000 and represents a continuation of earlier critical reviews up to 1988. Data tables containing the selected experimental Stark broadening parameters are presented with estimated accuracies. Guidelines for the accuracy estimates, developed during the previous reviews, are summarized again. The data are arranged according to elements and spectra, and these are presented in alphabetical and numerical order, respectively. A total of 77 spectra are covered, and the material on multiply charged ions has significantly increased. Comparisons with comprehensive calculations based on semiclassical theory are made whenever possible, since the comparison with theory has often been a principal motivation for the experiments.

Stark broadening and shift measurements of visible Si II lines

A set of experimental Stark width and shift parameters of visible singly ionizedsilicon spectral lines is reported in this paper. Measurements have been made on apulsed plasma generated in a linear discharge lamp filled with a mixture of silaneand helium. Electron density and temperature in this plasma range from 0.2 to0.9 × 1023 m−3 and from 16 000 to 20 000 K respectively. Electron density has beensimultaneously determined by two-wavelength interferometry and fromStark broadening of He I 501.6 nm, He I 728.1 nm and Hαlines. Temperature has been simultaneously determined from a Boltzmann plot ofHe I lines, from absolute emission of He I lines and from a Boltzmann plot of Si IIlines. Dependences of measured Stark parameters on electron density andtemperature have been investigated and the final results have been compared withmost of the previous experimental data as well as with some theoretical models.

On the Stark Width Regularities in Doubly Ionized Spectra

The existence of the Stark width dependence on the upper-level ionization potential of the quantum transition has been presented for twelve types of transitions in spectra of four doubly ionized atoms: N III, O III, S III and Cl III. On the basis of established regularities the Stark width values for 45 spectral lines, not measured or calculated before, have been predicted. A critical analysis of the existing experimental Stark width data is also given.

Temperature dependence of Stark width of the 463.054 nm N II spectral line

Stark width of the 463.054 nm singly ionized nitrogen spectral line, that belong to 3s 3p transi- tion, have been measured in a linear pulsed, low pres- sure, arc discharge. The working gas was helium-nitrogen- oxygen mixture. Electron densities of 0.75 10 23 m 3 to 1.45 10 23 m 3 were determined in the electron temper- ature range between 30 000 K 38 000 K. The measured values have been compared with our calculated data, us- ing the modied semiempirical approximation. On the ba- sis of the agreement among experimental and theoretical Stark width data, the isolated 463.054 nm N II spectral line can be recommended as convenient spectral line for plasma diagnostics.

STARK BROADENING PARAMETERS OF ANALOGOUS SPECTRAL LINES ALONG THE LITHIUM AND BERYLLIUM ISOELECTRONIC SEQUENCES

We report the results of theoretical and experimental study of the Stark broadening and shifting of analogous spectral lines along the lithium (3 s 2 S–3 p 2 P°) and beryllium (3 s 3 S–3 p 3 P°) isoelectronic sequences. For the evaluation of Stark broadening parameters the impact semiclassical method is used. The Stark widths and shifts along both sequences are measured in the plasma of a low-pressure pulsed arc. Plasma electron densities were determined from the width of the He II P α line while electron temperatures were measured from the relative line intensities. Both experiments agree within estimated uncertainties with our semiclassical results. Although the overall agreement between theory and experiments is found, gradual change of the discrepancy for the widths along the sequence is detected. The comparison of experimental Stark shifts with the theories shows that the magnitude and direction of line shifts along the Li-sequence may not always be predicted by theory. The comparison of experimental Stark widths along the Be-sequence for B II, C III, N IV and O V with semiclassical theory shows a similar tendency. The discrepancy with theory is large for the B II and it is improved for higher members of the sequence. The only measured Stark shifts for N IV and O V are of a different sign (red for N IV and blue for O V), and this change of sign along the sequence cannot be explained by the theory.