High density measurements of the Stark broadened profile of the He(II)4686 Å line

The Stark broadened profile of the He(II)4686 Å line has been scanned in the electron density range of 1–3 × 10¹⁸ cm^-3. The electron temperature, as determined from the line to continuum ratio, ranged from 9.4 to 19.9 eV. The plasma which emitted the He(II)4686 Å line was created in a 60-kJ theta pinch operated with a high fill pressure (3 and 5 torr) of pure helium. Electron densities were calculated from the half-half widths of the He(II)4686 Å line using two Stark broadening theories. These electron densities are compared with the electron densities determined from the absolute value of the continuum intensity and a total sweep up compressional model. The two theoretical models predict electron densities in good agreement with the electron densities from the absolute value of the continuum intensity.     

On the branching ratios of several pairs of He(II) lines

Branching ratios of He(II) lines have been measured for the principal levels 5–10. The observations have been made on an He plasma produced by a hollow cathode-arc discharge, having an electron density of 3×10¹⁹m^-3 and an electron temperature of 2×10⁵ K on the axis of the discharge.The observed branching ratios differ by about 30% from the ones following from theoretical transition probabilities, if the sublevels of the main levels were populated according to their statistical weights. The shape of the He(II) 4686Åemission line observed off the axis of the discharge using a Fabry-Pérot interferometer gave evidence of a non-statistical population distribution for the sublevels.     

X-ray spectroscopy of multiply-charged ions from laser plasmas

Original results are reported on the observation and identification of spectra of multiply-charged ions in the range of λ ≈ 1.5–15 Å, which corresponds to transitions with a range of principal quantum number n. The main part of the review consists of tables with about a thousand spectral lines, which have been mainly observed in laser-plasma radiation, as well as in the solar corona and other laboratory sources at an electron temperature T_e≈10⁷°K. The accuracy for the wavelengths (Δλ) is the following: Δλ is equal to ≈ 0.0005 Å for λ ≈ 2.5 Å and it is equal to ≈ 0.003 Å for λ ≈ 15 Å. The spectral lines are considered for the following transitions: 1-n type for [H]-like ions (Z = 11–16)and [He]-like ions (Z = 11–26); 2-n type for [Li]-like ions (Z = 19–26), [Be]-like ions (Z = 22–34) and [Ne]-like ions (Z = 26–42); 3-n type [Co]- and [Ni]-like ions (Z = 73). The line-list contains about four hundred wavelengths for multiply-charged iron L-ions (Fe(XVII)-Fe(XXIV)) and is presented with identification of some of the transitions. The wavelengths and intensities of satellites of the [H]-like ions and [He]-like ions, which are caused by transitions from the doubly-excited autoionization states 2l2l′ and 1s2l2L′ of [He]-like ions (Z = 11–16) and [Li]-like ions (Z = 11–26), respectively, are also considered.     

Oscillator strengths of ionized chromium lines in the 2413–2718 Å wavelength range

Oscillator strengths for one hundred and twenty-three Cr(II) lines, in the spectral region 2413–2718 Å, have been measured using a wall-stabilized arc. Chromium was introduced into the arc channel in a gas mixture containing Cr(ClO)₂, argon and helium. Diagnostic studies were carried out by a numerical solution of a set of equations which describes plasma properties for the case of partial LTE. The absolute scale was established by using the line 2672.83 Å of Cr(II) with accurately known ?-value. The measured oscillator strengths are compared with theoretical calculations. Discrepancies have been found to be greater than the experimental uncertainties.     

Oscillator strengths of ultraviolet V(II) lines (2290–2530 Å) from emission measurements in a stabilized arc

An argon-vanadium plasma has been produced in a wall-stabilized arc. The metal was introduced into the arc as an oxide powder suspended in flowing argon. Before introduction into the arc channel, the suspension was pulsed towards an auxilliary plasma source. The plasma radiation was photographed in the u.v. spectral region with a 10m concave grating vacuum spectrograph using an Eagle mounting. Relative calibration of the emulsions was carried out by using the intensities in the wings of the 2478 and 1931 Å lines of C(I) emitted by an Ar-CO₂ plasma; the primary standard radiation was provided by the continuum emitted from this plasma, which was produced in a stabilized arc. Plasma diagnostics were performed assuming LTE. Absolute gf-values for 33 V(II) lines in the range 2290–2530 Å have been evaluated using a computer program for statistical treatment of the data. Comparisons with theoretical calculations often show discrepancies that are larger than estimated experimental error limit.     

Measurements of electron density and Stark width of neutral helium lines in a helium arc plasma

Electron densities in an atmospheric helium arc plasma have been measured with the Stark broadening parameters of helium spectral lines. The spatially distributed radiation intensities are converted to plasma emission coefficients at every wavelength by means of Abel inversion. From the inverted profiles of He I lines of 4713 ?, 5016 ?, and 6678 ? electron density has been calculated, which ranges from 0.5 ×10¹⁶ to 4 ×10¹⁶ cm^-3 for a helium arc with current 200 A. Stark widths of He I lines of 3889 ? and 7065 ? are determined based on the measurements and compared with existing data.     

Distribution of Excited Atoms and Ions in a Plasma Generated at the Surface of Ferroelectric Ceramic

The distribution of excited atoms and ions in a plasma generated at the surface of ferroelectric ceramic has been studied. For all studied spectral lines of He I, Ar I, Ar II and hydrogen a decrease of the total line intensity with the increasing distance from the ceramic surface has been found. The shapes of these distributions are characteristic of the specific spectral lines. The distributions for He I lines depend strong on the concentration of argon in the helium — argon mixture. The effect of overpopulation of some excited Ar II ion levels in an argon discharge observed already in a previous work has been found also in the case of a helium — argon plasma.     

A shock tube study of line broadening in a temperature range of 6100 to 8300 K

Line widths of the Ca(II) 3968 Å and Na(I) 5890 Å resonance lines broadened by electric microfields in a plasma were measured. A pressure-driven shock tube was used as the light source. Radiation from the equilibrium region behind the reflected shock wave was studied using a rapid scanning Fabry-Perot interferometer. Electron and argon atom densities of about 8 x 10¹⁶ and 1 x 10¹⁹ per cm³, respectively, were achieved at the relatively low temperature of around 7500 K by vaporizing a cesium powder that had been added to the shock tube as a solid aerosol in argon gas. The measured line widths were predominantly Stark broadened by the electrons and ions in the plasma, although Doppler, van der Waals, instrument function and optical depth effects had to be taken into account. The electron broadened line width of Na(I) 5890 Å was lower by about 16% than the predicted value from a semiclassical calculation, in agreement with a recently reported measurement, while for Ca(II) 3968 Å the results agree with previous reliable experiments and are lower than two calculated values by 20 and 36% respectively. The van der Waals broadening by argon was also determined and showed qualitative agreement with other results.     

Oscillator strengths of ultraviolet V(II) lines from measurements in a vanadium-helium plasma

A V-He plasma has been produced in a well-stabilized arc. Oscillator strengths for 66 V(II) lines in the range 2342–2617 Å have been determined. Comparisons with theoretical values show large discrepancies for about 25% of the lines, possibly due to errors in calculations and in term classifications.     

Stark-width measurements of argon-ion lines with a Fabry-Pérot interferometer

Stark widths of optically thin line profiles of the 4806 and 4426 Å Ar(II) lines in an atmospheric cascade arc plasma have been measured with a Fabry-Pérot interferometer. These experimental results are significantly lower than all other experimental data and differ about a factor of 2 from theoretical calculations.     

Experimental study of stark broadening of nitrogen ion lines in a theta pinch plasma

We have studied the Stark broadening of the 3s-3p, 3p-3d and 3d-4f emission lines of the nitrogen II, III, and IV ions emitted from a hot plasma. The plasma was created by a 60 kJ, 60 kV single turn coil theta pinch, where the fill gas was 3 torr of (49%He+51%N₂). The plasma was diagnosed by measuring the Stark-broadened profile of the He(II) 4686 Å line and by taking shadowgrams of the plasma development. It was found that the ionization stage distribution and thus the electron density departed from that predicted by Saha-Boltzmann equilibrium relations. The analysis of the plasma parameters gave an electron density of 1.4 x 10¹⁸ cm^-3. The electron temperature was measured from the relative intensities of emission lines as well as from the line-to-continuum ratio and was found to be 5.0 eV. The line profiles have been fitted to Lorentzian profiles and the thus measure line widths are compared with earlier experimental data as well as with simple theoretical calculations. We find that our line widths are broader than earlier data taken at lower densities if we assume a linear scaling of the half width with the density. A simple Lorentzian profile fits in most cases quite well to the observed line profile. The simple calculations can predict the linewidths within 20% for the low lying levels of both the singly and doubly ionized nitrogen while the predictions are far too narrow for the higher lying levels from the multiply ionized atoms.     

Doubly excited states in the beam-foil Li spectrum

Beam-foil excited spectra of Li atoms and ions have been investigated in the wavelength range 2000–6000 Å. Line widths and lifetimes are given for the lines at 3155 Å, 3144 Å, and 5539 Å, the two latter representing transitions between doubly excited states.     

Observation of line radiation from highly charged Mo ions in a vacuum-spark plasma

Using a curved-crystal spectrograph of the transmission type the X-ray emission from a low-inductance vacuum-spark with Mo-electrodes has been investigated in the wavelength range 0.5Å<λ}<0.9Å. By means of a noise suppression technique, a number of weak lines have been resolved from the continuum. Comparing the measured wavelengths to results of relativistic energy level calculations these lines are identified as belonging to electronic transitions within singly excited heliumlike MoXLI ions and doubly excited lithiumlike MoXL ions. Continuum and line emission are used to estimate electron temperature and density.     

Laser oscillation at 4765 Å in a pulsed HeAr afterglow

Laser operation on transitions of Ar II was investigated in a pulsed HeAr discharge. Oscillation at 4765 Å in the afterglow indicates collisions between He 2³S metastables and ground state Ar ions being involved in obtaining population inversion.     

Spatial-temporal ion structures in the earth’s magnetotail: Beamlets as a result of nonadiabatic impulse acceleration of the plasma

The properties of high-energy ion beams (beamlets) observed in the boundary layer of the plasma sheet of the Earth’s magnetotail during short time intervals (1–2 min) have been considered. Beamlets are induced by nonlinear impulse accelerating processes occurring in the current sheet of the far regions of the geomagnetic tail. Then, moving toward the Earth along the magnetic field lines, they are detected in the magnetotail (in the plasma sheet boundary layer) and in the high-latitude part of the auroral zone in the form of short bursts of high-energy ions (with energies of several tens of keVs). The size of the localization region of the beamlets in the magnetotail and auroral zone has been determined by the epoch-superposition method, and it has been shown that beamlets are concentrated in a narrow region near the plasma sheet boundary, whose latitude size is no more than 0.8δ. This conclusion corroborates the theoretical prediction that the nonadiabatic resonant acceleration of ions occurs in a spatially localized region near the separatrix separating the open magnetic field lines and closed field lines, which contain the hot and isotropic plasmas of the plasma sheet. Based on the CLUSTER multisatellite measurements, the spatial structure of beamlets is analyzed and it has been found that the Alfvén wave arises due to the excitation of fire-hose instability at the instant of the exit of the ion beam from the current sheet to the high-latitude region of the far tail of the Earth’s magnetosphere. The longitudinal (along the magnetic field) and transverse sizes of a beamlet are estimated. It has been found that the beamlet is a dynamic plasma structure whose longitudinal size is several hundred times larger than its transverse size.     

Noise and output power in the CW 4416 Å HeCd laser

It is shown that the anomalous output power-discharge current dependence observed on a 50 Hz a.c. excited 4416 Å HeCd laser is due to the appearance of plasma oscillations, which cause an increase of He metastable density.     

Measurements of transition probabilities for doubly ionized vanadium

Transition probabilities of 43 doubly ionized V lines have been measured in the spectral range 2280–3600 Å. These lines belong to the 3d²4s–3d²4p transition array. Emission spectroscopy was used to obtain line intensities. The spectra were emitted from a He plasma with added VOCl₃ vapour in a wall-stabilized arc.     

The Broadening of He I lines including ion dynamic corrections,with application to λ4471Å

A theory is developed for the broadening of He I lines with forbidden components which is valid at low densities (where the forbidden line is reasonably well isolated). This theory takes into account the effects of dynamic ion broadening. Application to λ4471Å gives good agreement with experiment and with a recent calculation of Lee; reasons for agreement with Lee are discussed in detail. Comprehensive tables for 4471Å are presented. These have been extended further into the line wings than previous tabulations. Static ion theory is found to be adequate for densities greater than ～ 5 × 10¹⁵ cm^?3. A simple numerical profile for allowed lines, taking into account dynamic ion effects, is also presented.     

Characteristics of laser and current pulses in a He–SrCl2 vapor laser

An experimental investigation on the characteristics of laser and current pulses in a He–SrCl₂ vapor laser is carried out. The temporal dependences of the discharge current pulse on the laser pulses at the 1.09 μm, ～3 μm and 6.45 μm lines in strontium atoms and ions are measured and analyzed under different laser output powers. It is found that all laser pulses appear at the falling edge of the current pulse and shift forward to the current pulse with increasing laser output power.     

The growth and composition of anodic films on GaP

Anodic films have been grown on GaP in a variety of buffered anodizing solutions with pH ranging from 3 to 10. The films were grown at constant current densities from 1 to 100 mA/cm². Films with thicknesses in the range 500–1000 Å resulted from the higher current densities. The films were analyzed using the Rutherford backscattering of 1·7–2 MeV ⁴He ions in conjunction with ion channeling. This analysis revealed two distinct types of films; those with uniform composition as a function of depth and those with non-uniform profiles. The uniform films have Ga:P:O composition ratios typically ～1:2:5:8 whereas the non-uniform films have typical integrated Ga:P:O ratios of ～1:1·5:5. In the non-uniform films, which are the majority of those grown, Ga is piled up at the film-electrolyte interface; associated with this Ga excess is a corresponding P deficiency at the interface. This indicates that Ga migrates through the films during anodizing and forms a Ga-rich outer layer. In the uniform films it appears that much of the migrating Ga is continually being dissolved in the electrolyte during anodization.