Some regularities within the Stark widths of resonance lines of alkali-like homologous atoms and ions

Common regularities for the Stark widths of the resonance lines of neutral alkali-metal, singly ionized alkali earth-metal and B III, Al III, Ga III, In III and Tl III atoms and ions respectively have been found and discussed.     

Stark widths and shifts of several prominent Ne I spectral lines

Stark widths and shifts of six prominent Ne I spectral lines have been measured in linear pinch plasma sources and compared with existing theoretical and experimental results.     

Experimental Stark widths and shifts of two ultraviolet C(II) lines

Photoelectric measurements of Stark widths and shifts of the components of the C(II) multiplet UV13 at 2837 Å were made with a wall-stabilized arc in a gas mixture of argon, hydrogen and carbon dioxide. Plasma diagnostics have been carried out to determine the electron density and the temperature. For experiments performed under two different physical conditions, the values n_e(1) = 4.95 × 10¹⁶ cm^?3, T(1) = 11,430 K and n_e(2) = 6.78 × 10¹⁶ cm^?3, T(2) = 12,080 K were obtained. Agreement between our widths and experimental data of Plati?a et al. is within error limits; a discrepancy of a factor of 4 appears in a comparison of our data with those of Kusch.     

Stark widths of doubly- and triply-ionized atom lines

In this paper, we report modifications of well known semiempirical and semiclassical approximation furmulas for Stark line-width calculations. Comparisons with experiments for doubly ionized atoms yield, as an average ratio of measured to calculated widths 1.06 ± 0.31 for a modified semiempirical formula and 0.96±0.24 for a modified semiclassical formula. For triply ionized atoms these ratios are 0.91±0.42 and 1.08±0.41, respectively. Comparison with other theoretical calculations have also been made.     

Experimental measurements of stark shifts and widths of NaI and KI resonance lines

Stark broadening and shift parameters for resonance lines of sodium and potasium emitted by an electromagnetic T tube plasma were found to be in good agreement with theoretical data of Griem in a large range of temperature (15000 K – 26000 K).     

Stark broadening of the Al resonance lines

Absolute Stark-broadened profiles of the Al resonance lines (3p-4s, γ = 3961.5 and 3944.0 Å) have been measured under conditions of complete LTE in a conventional shock-tube. Plasma electron densities were determined by using a laser-interferometer. Uncertainties in the measurements (15% for the widths and 13% for the shifts) are discussed. The results are compared with impact-broadening calculations.     

Stark shifts and fine structure of the Li 3 D states

⁶Li 3²D _{3/2, 5/2} states were studied using a diode laser to first excite the 2P _3/2 state and a dye laser to populate the 3²D _{3/2, 5/2} states. The dye laser was modulated by an electro-optic modulator and intersected an atomic beam that passed through a field free region and subsequently through a uniform electric field. A value of 1084.24±0.20 MHz was found for the 3²D fine structure splitting. The scalar and tensor polarizabilities were determined to be α (3D _3/2 ) = - 3.753±0.015, α ₂ (3D _3/2 ) = 2.893±0.017, α (3D _5/2 ) = - 3.772±0.008 and α ₂ (3D _5/2 ) = 4.058±0.013 MHz/(kV/cm)². Received 26 September 2002 / Received in final form 22 January 2003 Published online 11 March 2003 RID="a" ID="a"e-mail: wlaser@yorku.ca     

Calculated stark widths of oxygen ion lines

Calculations have been performed on the electron impact broadening of isolated lines from singly-ionized and doubly-ionized oxygen emitted from a plasma of electron density 10¹⁷ cm^-3 and temperature about 2 eV. These have been compared with results of measurements performed by Plati?a, Popovi?, and Konjevi? on a plasma produced by a low pressure pulsed arc. Good overall agreement has been obtained for both ionization stages, which we interpret as strong support for a recently derived expression for the effective Gaunt factor in line broadening calculations. This in turn indicates the important role that the curvature of the perturber trajectory plays in the broadening process, and that by proper allowance for this effect, classical path calculations of the isolated ion line widths can be extended to spectra of the multiply-charged ions. Some ambiguity still remains, however, as to the proper method of extrapolation of the effective Gaunt factors below threshold energies in the classical path calculation of the elastic contribution to the broadening. The present comparison appears to indicate that for the higher ionization stages, extrapolation of ? as a constant equal to its threshold value, is satisfactory.     

Theoretical calculation of electron impact widths and shifts of XeII lines

Summary The shifts and widths of prominent XeII transitions are calculated in the semi-empirical approach; a very good agreement with experimental values is obtained. The oscillator strengths were calculated using complete intermediate coefficients after energy matrix diagonalization. The author of this paper has agreed to not receive the proofs for correction.     

Estimates of Stark broadening of oxygen ion lines

Recent measurements of spectral line widths for singly- and doubly-ionized oxygen atoms, are compared with the corresponding values predicted by the semi-empirical method of Griem. On the basis of these results, as well as a similar comparison for singly- and doubly-ionized nitrogen atoms in a recent paper, we propose some “experimental” values of the threshold Gaunt factors for these ions.     

Estimates of Stark broadening of nitrogen ion lines

Recent measurements of spectral line widths for singly- and doubly-ionized nitrogen atoms, are compared with the corresponding values predicted by the semi-empirical method of Griem. The overall agreement, for representative transitions from 6 multiples of N(II) and 3 multiplets of N(III), tends to confirm the usefulness and general validity of Griem's approach.     

Calculated Stark widths of isolated S(III) and S(IV) lines

Calculations have been performed on the electron-impact broadening of isolated lines from doubly-ionized and triply-ionized sulphur emitted from a plasma of electron density 10¹⁷ cm^-3 and temperature 28,500°K. These have been compared with results of measurements performed by Plati?a, Popovi?, Dimitrijevi?, and Konjevi? on a low-pressure, pulsed arc. Good overall agreement has been obtained for both ionization stages, in confirmation of our earlier conclusions based on a similar comparison for oxygen ion lines. The present calculations have been compared with calculations based upon two simplified models of Griem and the classical-path approximation of Sahal-Bréchot. Our calculated widths are in better agreement with experiment than with values obtained from the first two models; for the two multiplets, where comparison is possible, good agreement is found with the widths obtained by Sahal-Bréchot. We conclude that the present model, whereby the effective Gaunt factor is calculated, is capable of predicting reliable values for the Stark widths of isolated ion lines. Comparison with experiment [for S(III) indicates that, provided a sufficiently complete set of perturbing levels is used in the calculations, the present formula for ? may also be used for below-threshold energies in the determination of the elastic contribution to the broadening. For S(IV), an ambiguity remains in this regard, owing chiefly to a scarcity of available experimental data.     

Stark profiles of some ion lines of alkaline earth elements

The widths and shifts of Mg⁺, Ca⁺, Sr⁺ and Ba⁺ lines broadened by electron and ion Stark effects have been measured in an argon welding type plasma. The electron density is about 1.3×10¹⁷ cm^-3 and the temperature is about 13,000°K. Special care was taken to avoid self-absorption of resonance lines. Injection of alkaline earth elements into the cold region of the plasma edge permitted reliable measurements of the signs of line-shifts. Experimental results are compared with semi-classical theories and a new-classical computation of Sahal-Bréchot in which resonances of elastic cross sections are taken into account. Good agreement is observed between experiment and the later calculations.     

Stark shifts of some isolated spectral lines of singly ionized earth alkaline metals

Stark shifts of spectral lines of singly ionized earth alkaline metals have been measured behind the reflected shock wave produced in an electromagnetically driven “T” tube. The results are compared with theoretical values computed using Griem's semiempirical formula³. The agreement is generally poor.     

On the Stark broadening of Sr+ and Ba+ resonance lines in ultracold neutral plasmas

We report results of the Stark broadening calculations for Sr⁺ and Ba⁺ resonance lines in ultracold plasmas using semiempirical formulas and numerical computer simulation technique. The simulation results show that strong collisions dominate Stark broadening at very low electron temperatures and weak collision approximation used recently by Vrinceanu et al. cannot be applied in this temperature region. Consequently, the temperature trend of Stark widths and shifts changes from successfully used at elevated temperatures to an increasing trend with temperature, which is characteristic for strong collisions at low temperature.     

Stark widths and transition probabilities of some multiplets of singly ionized carbon

Photoelectric measurements of lines emitted by a helium-carbon d.c. arc plasma of n_e = 1.9 × 10¹⁶cm^-3 at T = 12,800 K have been performed. Stark widths of 6 C(II) lines and transition probabilities for components of 3 C(II) multiplets were determined and compared with other experimental and theoretical data. Good agreement was generally observed except for the C(II) multiplets UV13 and UV14, where the results of Kusch deviate notably from others.     

Excitation of resonance lines of the cadmium ion by monoenergetic electrons

The excitation of resonance lines at 226.5 and 214.4 nm, corresponding to the transitions 226.5 (5p ² P ₁ ^2/0 →5s ² S _1/2) and 5p ² P ₃ ^2/0 → 5s ² S _1/2, respectively, in the Cd⁺ ion upon collisions with monoenergetic electrons with an energy in the range of 4–130 eV is studied with high precision by a spectroscopic method in crossing beams. It is found that the dependence of the effective excitation cross sections of the resonance doublet components on the energy of the electrons has a distinct resonance structure. It is shown that the dominant mechanism responsible for this structure is the capture of an incident electron by a Cd⁺ ion with the simultaneous excitation of an electron from the subvalence 4d ¹⁰ shell to the autoionizing states of the Cd atom with their subsequent decay (directly or via cascade transitions) to resonance levels of the ion. The results obtained are compared with data from other experiments and with the results of the R-matrix strong-coupling calculation of 15 states and of semiempirical calculation using the Van Regemorter formula.