N. Konjević

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.

Plasma diagnostics of the Grimm-type glow discharge

Abstract Results of argon-hydrogen plasma diagnostics in the plane cathode Grimm-type glow discharge are presented. Radial distributions of electron excitation temperatures, electron density and temperature of excited hydrogen atoms are reported. A numerical procedure necessary for the evaluation of the electron density and the temperature of excited hydrogen atoms from the profiles of hydrogen Balmer lines has been developed. The algorithm can be applied to the sum of an arbitrary line profile if they are convolved with a Gaussian profile.

Excessive Balmer line broadening in a plane cathode abnormal glow discharge in hydrogen

Results of a Doppler spectroscopy study of the hydrogen Balmer alpha line in an abnormal glow discharge operated in pure hydrogen are reported. Measurements of line shapes are performed side-on to the discharge axis in a low electric field region of negative glow. The excessive Balmer alpha broadening is detected and its presence and linewidth is related to the collisions of fast hydrogen atoms with molecular hydrogen. The collision model enabled also an estimation of effective cross section data from the Balmer alpha axial intensity decay curves. Large excessive Balmer alpha line broadening in pure hydrogen and its dependence upon the direction of observation with respect to the electric field is in contradiction to the resonance transfer model, proposed byMills et al. in several publications [see, e.g., IEEE Trans. Plasma Sci. 31, 338 (2003)].

Doppler spectroscopy of hydrogen and deuterium Balmer alpha line in an abnormal glow discharge

The results of hydrogen and deuterium Balmer alpha line shapes and line intensities study in an abnormal glow discharge are reported and analyzed. The Doppler shifts along line wings are used to determine energies of excited hydrogen and deuterium atoms. For 12 different cathodes, intensity and shape of line wings are examined and dependence upon cathode material is determined. Tentative explanation of line wings intensity dependence is related to the sputtering of cathode material and back-scattering coefficients of incident hydrogen or deuterium ions and atoms from cathode surface. The influence of the light reflected on a cathode surface to the line shape measurements along discharge axis is considered. In hydrogen, deuterium, and Ar+3%H/sub 2/ discharges, basic mechanisms of fast hydrogen generation and excitation are studied. The shape and intensities of the H/sub /spl alpha// line profiles in pure hydrogen and in argon-hydrogen mixture may be correlated with hydrogen atom-carrier gas collision excitation cross sections. In order to assess the importance of reflected fast hydrogen atoms back scattered from the cathode surface, for the Balmer line shape formation, a simulation program is used. The results are in a qualitative agreement with Balmer line shapes observations.

Electric field measurement in the cathode fall region of a glow discharge in helium

Spatial distribution of electric field strength in the cathode fall region of an analytical glow discharge in helium and helium-hydrogen mixture is determined from the Stark splitting and shifting of three visible helium lines and their forbidden components. For this diagnostic technique the basic theory is outlined. The results in gas mixture agree well with electric fields determined from the shape of Hβ line.

A program for the evaluation of electron number density from experimental hydrogen balmer beta line profiles

Abstract A program for the determination of plasma electron number density, 1020≤(Ne)≤1023 m−3, from the comparison of experimental and theoretical hydrogen Balmer beta (Hβ) line profiles is described in detail. Three theoretical data sets (one set is calculated within the framework of this paper) are included with the program and may be selected as a users choice. Apart from Ne determination from the comparison of the whole experimental and theoretical profiles, this program offers a fast estimation of Ne from the halfwidth of the experimental line shape. If necessary, certain parts of the experimental profile may be neglected in the procedure of comparison with theory. This possibility enables the use of noisy line shape recordings for Ne determination. The Hβ asymmetry study may be carried out by generating the difference between experimental and best-fitted theoretical line profiles.

Regularities in Experimental Stark Shifts

Abstract We have examined regularities in plasma-produced line shifts (Stark shifts) by a comprehensive analysis of literature data. Since the shifts are the result of atomic collision processes, regularities are expected from general atomic structure considerations. Specifically, systematic behavior should occur for spectral series and for corresponding transitions in homologous atoms and isoelectronic ions. Also, Stark shifts should be similar for lines within multiplets and, to a lesser degree, within supermultiplets and transition arrays. Numerous examples show conclusively that the measured data exhibit these predicted regularities. When pronounced irregularities occur, they are readily explainable in terms of special circumstances in the atomic structure.

Excessive Balmer line broadening in microwave-induced discharges

Results of a hydrogen Balmer line-shape study on microwave-induced plasma discharges operated with pure hydrogen and with argon–hydrogen or helium–hydrogen mixtures are reported. Plasma is generated in a rectangular or coaxial microwave cavity in two separate experiments. In both cases, the emission profiles of the Balmer lines did not show excessive broadening as reported by Mills et al. [J. Appl. Phys. 92, 7008 (2002)].

Parametric study of an atmospheric pressure microwave-induced plasma of the mini MIP torch } I. Two-dimensional spatially resolved electron-number density measurements

Abstract The results of spatial distribution measurements of the electron-number density, N e , in an atmospheric pressure microwave-induced plasma in argon are presented. Electron-number density is determined from the width of the hydrogen H β 486.13-nm line. The influence of the microwave input power in the range 80–150 W on the spatial distribution of N e is first determined. For the selected input power of 100 W, the influence of molecular hydrogen in wet and desolvated nebulizer and support gas, and the corresponding changes in the electron density distributions are studied. The influence of potassium as a low ionization-potential element on the spatial distribution of N e is also studied, with the result that a considerable lowering of the electron number density is detected.

On the atomic hydrogen line shapes in a plane-cathode obstructed glow discharge

In order to investigate the charge-transfer reaction between Ar+ and H2 which is important for the shape of hydrogen Balmer lines and to clarify the pathway of this reaction, the study of charge-transfer reaction Ar+ + Cu in argon-copper, argon-copper-hydrogen and neon-copper-hydrogen plasma of a plane-cathode hollow anode glow discharge was undertaken. It is shown that Ar+(2P1/2) + H2 reaction is the main source of H2+ ions in our plasma. Study of the influence of cathode material on the shape of hydrogen Balmer lines clearly shows that the lower part of these lines emitted by the discharge in hydrogen and in the mixture of hydrogen and neon are appreciably broadened. Analysis of these profiles indicates that scattering and excitation of hydrogen on the sputtered cathode material in the vicinity of the cathode plays an important role in line shape formation.