Stark broadening parameters of the 381.96 nm He I line

Stark width (W) and shift (d) of the neutral helium (He I) 381.96 nm spectral line in the high lying 2p-6d transition has been measured in the optically thin linear, low-pressure, pulsed arc discharge operated in the helium at 50 000 K electron temperature and 6.1 x 10²² m^-3 electron density. These values are the first experimentally obtained W and d related to this line. Unfortunately, comparison with theoretical results is not possible due to the fact that only one existing theoretical calculations has been done at a 10¹⁹ m^-3 electron density only. We have found negative line shift (toward the blue) that agree well with existing theoretical predictions.Received: 19 February 2004, Published online: 4 May 2004PACS: 52.70.Kz Optical (ultraviolet, visible, infrared) measurements - 32.70.Cs Oscillator strengths, lifetimes, transition moments - 32.70.-n Intensities and shapes of atomic spectral lines     

On the Stark broadening of the He I 447.1 nm spectral line

Characteristics of the Stark broadened and overlapping 447.1 nm He I spectral line and its forbidden 447.0 nm components have been measured at electron densities between 4.4×10²² m^-3 and 8.2×10²² m^-3 and electron temperatures between 18 000 K and 33 000 K in plasmas created in five various discharge conditions using the low pressure pulsed arc as an optically thin plasma source operated in helium-nitrogen-oxygen gas mixture. Good agreement was found among our measured line characteristics and their existing calculated values, based on the quasistatic approximation. Possible influence of the singly ionized oxygen impurity atoms (O II) on the intensity values of the dip between allowed and forbidden components was found that can explain the disagreement among some existing experimental and calculated line characteristics data, at higher electron temperatures and densities. On the basis of the observed asymmetry of the 447.1 nm spectral line profile we have obtained the ion contribution parameter at 10²² m^-3 electron density and 8 000 K electron temperature. Received 20 February 2001 and Received in final form 25 April 2001     

The He I 706.52 nm line shape characteristics in the plasma diagnostics

On the basis of the precisely recorded 706.52 nm He I line shape we have obtained the basic plasma parameters i.e. electron temperature (T) and electron density (N) using our new line deconvolution procedure in the case of five various plasmas created in a linear, low-pressure, pulsed arc discharge. Plasma parameters have been also measured using independent experimental diagnostical techniques. Excellent agreement was found among the two sets of the obtained parameters. This enables our deconvolution procedure to recommendation for plasma diagnostical purposes, especially in astrophysics where direct measurements of the plasma parameters (T and N) are not possible. Besides, on the basis of the observed asymmetry of the Stark broadened line profile we have obtained its ion broadening parameter (A) caused by influence of the ion microfield to the line broadening mechanism and also the influence of the ion dynamic effect (D) to the line shape. Our A and D parameters represent the first data obtained experimentally using the line profile deconvolution procedure. We have found stronger influence of the ion contribution to the 706.52 nm He I line profile than the existing theoretical approximations estimate. This can be important for plasma modeling or for diagnostics. Received 30 October 2002 Published online 15 April 2003 RID="a" ID="a"e-mail: vladimir@ff.bg.ac.yu     

Collisional broadening of Ba I line (553.5 nm) by He or Ar

The Doppler-free line shape of the 6s ^{2 1} S ₀ – 6s ¹6p ^{1 1} P ₁ transition at 553.5 nm in natural Ba in the presence of an argon or helium buffer gas has been measured at 744 K for gas pressures from 0.2 to 100 Torr. Using the measured data for pressures above 5 Torr, the broadening rate coefficients for the half width at half maximum (HWHM) are determined to be (4.9±0.5)10^–9 and (5.0±0.5)10^–9 s^–1 cm^–3 for helium and argon respectively.     

Valence electron spectroscopy using polarized He I radiation

Electron spectroscopic measurements by means of polarized He I radiation are presented. Polarization better than 97% is achieved by a fourfold reflection polarizer. Asymmetry parameters β are given for Kr and C₆H₆.     

Inhomogeneities in the shape of the He 504.7 nm line excited in a hollow cathode discharge

The profile of the He 504.7 nm line emitted in the negative glow of a hollow cathode discharge is analyzed as a function of the distance from the emitting volume to the cathode axis. The value of the discharge current varied within the range of 10–30 mA, the helium pressure being 0.4–1.5 torr. A dependence was found of the Voigt parameter a on the location of the emitting volume. The simultaneous recording of two line shapes, emitted from different regions of the discharge, enables us to observe a shift δv of the line center observed off-axis compared with the line emitted along the axis. The electric field intensity at the periphery, 6 mm off-axis, is evaluated on the assumption that Starkbroadening is the cause of δv.     

Calculation of the self-absorption of laser induced Mg I 285.2127 nm spectral line

In order to study the self absorption of laser induced plasma, using the escape factor, we study the self absorption of laser induced magnesium plasma at 285.2127 nm in this paper. The theoretical total radiance, the escape factor and the real radiance for Gaussian and Lorentzian profiles are discussed. The self-absorption of the Mg I 285.2127 nm line is explained, and some useful conclusions are drawn. This study is significant in the analysis of self-absorption of laser induced plasma.     

Use of multibeam interferometry to determine the refractive index of liquids

Journal of Applied Spectroscopy -     

Relativistic corrections to electron scattering by 2H, 3He,and 4He

Relativistic corrections to the scattering of electrons by a nonrelativistic nucleus are calculated, using the method of Close and Copley, and Krajcik and Foldy. Particular attention is paid to the deuteron, ³He and ⁴He. It is found that these corrections are substantially the same as those calculated by F. Gross for the deuteron. The corrections to ³He have the effect of moving the diffraction minimum, as calculated in a nonrelativistic model, outward by as much as 0.32 fm^?2. Smaller corrections are found for ⁴He.     

Structure of the 534.1 nm manganese laser line

The structure of the 534.1 nm manganese laser line and its temporal evolution emitted from a Mn/MnCl₂ vapor laser were measured and compared with the calculated atomic linshape of spontaneous emission. A brief interpretation of the laser line-shape has been suggested. It is found that the monochromaticity of the 534.1 nm line can be improved from the choice of the reservoir temperature and buffer gas pressure. The sequence of appearance of these peaks of the laser lineshape is governed by the intensity of the hyperfine components of the spontaneous emission.     

Two-electron description of electron transfer in He++He+ collisions

Electron transfer in He⁺ + He⁺ collisions is studied within the two-electron form of the atomic-orbital expansion method. The population of both singlet and triplet helium states is considered. The calculated total and partial transfer cross sections agree well with available experimental data. Deviations from results of other calculations and the transfer mechanism in the triplet channel are discussed.     

Calibration of excitonic photoluminescence to determine high aluminum concentrations in silicon

The photoluminescence spectroscopy method for determining the concentration of shallow acceptors or donors in silicon is extended for the case of aluminum. A calibration function of the photoluminescence intensity ratio of the aluminum bound exciton Al_TO(BE) and the free exciton I_TO(FE) is reported in the aluminum concentration range of 10¹⁵–10¹⁷ atoms/cm³ and in the temperature range of 15 K < T < 27 K. It is described as Al_TO(BE)/I_TO( FE) = 10^–15.1 × c_Al^0.84 × e^5.9meV/kT.

     

Study of a lidar for measurement of thermospheric He I 1083 nm for Lorentzian profile

Using the lidar backscatter cross-section and the normalized Lorentzian profile, we investigate the backscatter cross-section and the returned signal of He I 1083 nm for the Lorentzian profile theoretically. Taking the average temperature and pressure, we find that the backscattering cross-section for Lorentzian profile is larger than that for Gaussian profile near the line center, while is smaller than that for Gaussian profile far away from the line center. Through simulation, we find that the returned signal is strong enough for measurement of thermospheric metastable helium. This investigation is significant in the thermospheric metastable helium by lidar.     

Hyperfine structure and isotope shifts in 733.2 nm mixed forbidden line of Pb I

Studies of the hyperfine structure and isotope shifts in 733.2 nm mixed (M1+E2) multipole line of Pb I are presented. As a light source the electrodeless discharge tube was used. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with a CCD camera used as a detector. In the analysis of the spectra a computer simulation technique was used. The experiments with the isotope ²⁰⁷Pb yielded the hyperfine structure splitting constant A for the ³P₁ and ¹D₂ levels of the 6s²6p² ground configuration. In the experiment with natural lead the isotope shifts between four stable isotopes (204, 206, 207, 208) were measured.     

M1-E2 interference in the Zeeman effect of the 461.5 nm line of Bi I

Studies of the interference effect in the mixed-type forbidden line 461.5 nm are reported. A special computer program considering the M1-E2 interference was designed to obtain the predicted contour of the Zeeman structure of the line. By variation of free parameters, describing the line shape and the electric-quadrupole admixture, the calculated profiles were fitted into the recorded spectra. The E2 admixture found is (7.4± 0.4)%. Our result is compared with recent theories and other experiments.     

An algorithm to determine electron energy distributions from synchrotron radiation measurements

An algorithm to unfold the energy distribution function of a weakly relativistic, magnetically confined electron cloud from its emitted synchrotron radiation is described and applied to experimental data.