Determination of the Electron Density in an Argon Laser Plasma by Spectroscopy of the Hydrogen Hα and Hβ Lines

From measurements of the H_α and H_β spectral line profiles in a plasma, a method is developed which allows to separate the contributions of Doppler and Stark broadening. This method is superior to the deconvolution of Voigt profiles, in particular, when the lines are of low intensity. The electron density in the plasma can be calculated from the Stark broadening. An example is the low pressure (p ≈ 1 hPa) arc discharge of argon ion lasers which is characteristised by electron densities of approximately 10¹⁴ cm^?3 at heavy particle temperatures of about 10⁴ K. These plasma parameters lead to a broadening of the Balmer H_α and H_β spectral lines of hydrogen, which has a low concentration within the discharge area. The spectral lines are broadened due to the electron density dependent Stark effect and the temperature responsive Doppler effect. The results are consistent with predictions of the argon ion laser modelling.     

Anomalous Electric Fields Inside a Dense Plasma of a Current Sheet

For the first time there have been analyzed profiles of electric-field-sensitive n_a spectral lines of the Li-like impurity ions CIV, NV, OVI emitted by a hot dense plasma of a plane current sheet. Theoretical profiles of these lines have been calculated with an allowance for Anomalous Electric Fields (AEF). By comparing the experimental and theoretical profiles of the lines it has been established for the first time that in the plane current sheet there were developed AEF of rms strengths F₀ ≈ (100–120) kV/cm in the time interval from τ = ?0.2 μs to τ = 0 (the time τ was counted from the instant of the maximum intensity of the spectral line OVI 5291 Å). These results have been backed up by a similar analysis of the experimental profiles of the spectral line HeII 4686 Å of the primary gas of the discharge. The AEF reached these strengths at the same instant of time, τ = ?0.2 μs, when electron and ion temperatures reached their maxima: T_e ? 100 eV, T_i ≈ 300 eV. The instant τ = ?0.2 μs corresponds to a transition from the metastable stage to the explosive phase of the current sheet evolution. At this time the ratio of the AEF energy density to the thermal energy density of the plasma was § ≡ F²₀/[8π/N_eT_e + N_iT_i)] ≈ 10^?3, which exceeded a similar ratio for the thermal wave field by three orders of magnitude.     

Non-Equilibrium Effects in He-Ar-H Arc Plasma

A plasma composed by helium, argon, and hydrogen in a cascade arc of MAECKER-SHUMAKER type was examined in this paper. The spectrum of the studied plasma was recorded on the spectral plates by means of a STE 1 spectrograph. A photographic spectrophotometry method was used to determine the intensity and profiles of selected HeI, ArI, ArII, and H lines. On the grounds of the experimental results a spectroscopic diagnostics of the studied plasma has been made using different methods. It was found that there are the non-equilibrium effects in those plasmas. Observed diversions from the local thermodynamic equilibrium (LTE) could be explained on the grounds of the partial LTE model given by DRAWIN.     

Manifestation of outgoing resonance in stokes and anti-stokes spectra of ZnTe and ZnMgTe quantum wires

The spectra of resonant light scattering by ZnTe quantum wires have been measured at excitation energies of 2.18–2.72 eV. The quantum wires have been grown on Si(100) and GaAs(100) substrates by molecular beam epitaxy. The effect of outgoing resonance with the electron transition energy E ₀ on the intensity of phonon lines of the Stokes spectrum and on the intensity ratio of the Stokes and anti-Stokes spectral lines has been studied. The energy E ₀ has been determined in ZnTe and ZnMgTe quantum wires from the edge luminescence spectra.     

Tunable diode laser measurements of absolute linestrengths in the HNO3 ν2 band near 5.8 μm

Absolute linestrengths of selected lines in the υ₂ band of HNO₃ have been measured using a tunable diode laser spectrometer operating in a sweep integration mode. The direct measurement technique has been employed to obtain line intensities at 296 K for 22 isolated lines in the 1720–1725 cm^-1 region. The reported linestrengths have estimated uncertainties of 4%, a significant portion of this uncertainty arising from spectral interference from hot band transitions. From these linestrength measurements, an integrated band intensity of 1375 cm^-2-atm^-1 at 296 K is inferred.     

Determination of the Local Parameters of a Cascade‐Arc Plasma by the Profiles of the Lines in the Radiation Spectrum

The transverse distribution of the plasma temperature in the positive column of a d.c. cascade arc in argon at atmospheric pressure has been measured. The measurements have been carried out by the conventional method involving the determination of the emissivity of plasma as well as directly from the radiation spectrum of the arc without recourse to the Abelian inversion. A theoretical and model justification of the applicability of the second method is given. The results of the determination of the temperature profile in the observation direction by the width and shift of the ArI 425.9nm line selected for the diagnostics are presented. An analysis of the data obtained supports the possibility of determining the temperature of an inhomogeneous, optically thin plasma from the profiles of lines in the emission spectrum.     

Mechanisms of the destruction of micron conductors by an electromagnetic pulse with a subnanosecond front

The results of the experiments on the destruction of micron-diameter conductors by an electromagnetic pulse, which is generated in an inhomogeneous coaxial line by a high-voltage power source and has a subnanosecond front, are reported. The role of electrodynamic processes in the surface layer of microconductors and in environment in the formation of the spatial structure of the plasma channel and in the transformation of the energy of the source to the energy of radiation has been revealed. The spectral characteristics of the radiation of the plasma channel have been analyzed. It has been shown that the radiation spectrum at the time of the formation of the plasma corona is continuous. The most intense spectral lines of copper (510.554, 515.324, 521.82 nm) appear at ∼3 ns after the formation of the plasma corona. The temperature has been estimated from the ratio of the intensities of the spectral lines as T _e ∼ 0.7 eV.     

NH3 self-broadening coefficients in the ν2 and ν4 bands and line intensities in the ν2 band

Self-broadening coefficients of NH₃ in the ν₂ and ν₄ bands and absolute line intensities in the ν₂ band have been measured at room temperature for some selected lines in the P- and R-branches. Using a Fourier transform spectrometer, line intensities and collisional widths were obtained by fitting Voigt profiles to the measured shapes of the lines. The results of self-broadening coefficients are in reasonable agreement with calculated linewidths using a semiclassical model which reproduce rather well the systematic experimental J and K quantum numbers dependencies. Satisfactory agreement was also obtained for line intensities with previous measurements in the ν₂ band. From the intensity measurements, we have determined effective transition dipole moments as well as Herman–Wallis parameters for the ν₂ band.     

Radiation damping in an anharmonic oscillator

The effect of radiation damping in an anharmonic oscillator has been calculated using the technique of Kryloff and Bogolituboff. It is found that the intensity distribution of the emitted spectral line is asymmetric about its intensity maximum. The index of asymmetry agree with the experimental data on x-rayK _{a 1,2}lines.     

Optical emission spectroscopy investigation of sputtering discharge used for SiOxNy thin films deposition and correlation with the film composition

The r.f. discharge of sputtering silicon target using argon-oxygen-nitrogen plasma was investigated by optical emission spectroscopy. Electronic temperature (T_e) and emission line intensity were measured for different plasma parameters: pressure (from 0.3 to 0.7 Pa), power density (0.6-5.7 W cm⁻²) and gas composition. At high oxygen concentration in the plasma, both T_e and the target self-bias voltage (V_b) steeply decrease. Such behaviour traduces the target poisoning phenomenon. In order to control the deposition process, emission line intensity of different species present in the plasma were compared to the ArI (λ = 696.54 nm) line intensity and then correlated to the film composition analysed by Rutherford Backscattering Spectroscopy.     

Analysis of an Inhomogeneous Semitransparent Plasma by the Lines in the Emission Spectrum

Using the methods of numerical simulation, we have investigated the dependence of the intensity and parameters of the spectral line profiles in the radiation of semitransparent plasma on its optical thickness, the degree of inhomogeneity, and the parameter distribution. As a model, we used the equilibrium plasma of argon with a given temperature profile on the observation line. The calculation has been performed for the spectral lines of the argon atom characterized by different broadening constants. On the basis of the results obtained it has been shown that it is possible to diagnose the plasma and determine the degree of its inhomogeneity and reabsorption by the parameters of the self-reversed profiles of the spectral lines. To diagnose the plasma in the absence of self-reversal, we propose to use the line intensities in the emission spectra of the plasma, including those obtained by probing it by its self-radiation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 404–411, May–June, 2005.     

Study of the dependence of the radiative properties of high-frequency electrodeless lamps in an Hg-Ar mixture on the pressure of mercury vapor

The radiative characteristics of high-frequency electrodeless lamps in a mixture of mercury and argon have been studied theoretically and experimentally as functions of the cold spot temperature (the pressure of mercury vapor). The intensity of the mercury lines at 404.7, 435.8, and 546.1 nm, corresponding to the triplet transition (7³ S ₁-6³ P _0,1,2) in the visible spectral region, as well as the intensity of the UV resonance line (6³ P ₁-6¹ S ₀) at 253.7 nm, has been measured. A model describing the physical processes in the discharge plasma and including the kinetics of excited states of mercury and argon atoms has been suggested. The parameters of the discharge plasma and the electromagnetic field have been calculated self-consistently through the numerical solution of the system of equations of electron density and energy balance and population balance of excited levels of argon and mercury atoms, as well as the Maxwell equations. The model developed has allowed us to calculate the intensities of the mercury emission lines at 253.7, 404.7, 435.8, and 546.1 nm and to compare the results with experimental data. The relative intensities of the mercury spectral lines corresponding to the triplet transition 7³ S ₁-6³ P _0,1,2 have been calculated for the first time on the basis of a self-consistent model of the discharge.     

On the Cd III spectrum in a pulsed helium discharge

On the basis of the spectral line intensity relaxation during the plasma decay, fifty six spectral lines between 219 nm and 330 nm in the cadmium (Cd) spectrum were identified as Cd III (doubly ionized) or Cd IV (triply ionized) lines. The measured Stark widths of twelve, the most intense spectral lines around 315±15 nm with well defined profiles, are presented. Investigated spectral lines originate from the high lying energy levels, not classified up to now. A linear low-pressure pulsed arc was used as an optically thin plasma source. A pulsed discharge was produced in a pyrex discharge tube. Helium was chosen as the carrier gas. The cadmium atoms were sputtered from the thin cadmium cylindrical plates located in the homogeneous axial part of the discharge tube. The helium plasma was operated at electron temperatures up to 19 000 K and 1.1 × 10²³ m^-3 electron density. The stepwise ionization processes via the high lying singly ionized (Cd II) energy levels, populated well due to the Penning and charge exchange effects, provide high density of the Cd III (and Cd IV) ions in our helium plasma. The temporal evolutions of the spectral line intensities were monitored using a spectrograph and an ICCD camera as a highly sensitive detection system.     

Influence of Spectral Line Deconvolution on Measurement of Excitation Temperature in a Wall‐Stabilized Thermal Plasma by Optical Emission Spectroscopy

Abstract

The measurement of temperature in a wall‐stabilized thermal plasma is done by optical emission spectroscopy. The absolute intensity line method, relative intensity line method, and plot of the Boltzmann function are used. Another method, based on the measurement of electron density and calculations of concentrations, is also used. The influence of spectral line deconvolution on temperature profiles is studied. The results obtained by the four methods are compared. The influence of others parameters, such as the accuracy of spectroscopic constants, and the influence of the theoritical calculations of concentrations are also discussed. These methods employ Ar I, C I and O I lines to measure the temperature of an Ar–CO₂ mixture plasma produced in a wall‐stabilized arc.     

The Study on the Arc Plasma Temperature Measurement by Optical Emission Spectroscopy with Fiber Optical Transmission

Abstract

A method for transmitting radiation of the arc plasma with multimode fused quartz fiber onto the spectrograph has been studied. The plot of the Boltzmann function in emission spectral analysis is used for measuring temperature of the arc plasma. The measured temperature of the arc plasma is 5946.6K from least square linear regression of ln[λI/(gA)] and E_i for a number of the emission line intensities of the excited copper atom. Its regression coefficient and measured precision are ?0.97% and 1.7%, respectively. The advantages of the method of the diagnostic temperature for the arc plasma are absolute measurements of the temperature, remote sensing, precision and suitable for mal-environment, such as high temperature, toxic, explosion, strong magnetic or/and electrical fields.

In addition, we have discussed the effect of the spectroscopic constants, such as transition probability, A , the statistical weight of the upper level, g , and the energy of the upper level, E_i , of copper lines on calculating temperature with a plot of the Boltzmann function in detail. The results show that the accurate measurement of the temperature for the arc plasma is obtained only when the spectroscopic constants are selected correctly.     

Spectroscopical Observation of a Relaxing High Speed Nitrogen Plasma Jet

A near sonic nitrogen plasma jet operating at pressures between 100 Torr and 1 atm has been investigated spectroscopically. From the absolute emission coefficient of a NI spectral line, local values for the electron temperature T_e have been derived. For pressures above 200 Torr, T_g was found to coincide within the limits of experimental error with the gas temperature T_g. The latter quantity has been determined via the relative emission coefficient of selected rotational line components of the N₂⁺ molecular band at 3914 Å. The results of these measurements together with control data for the electron density derived from the continuous emission coefficient indicate that at pressures above 200 Torr the existence of a thermal equilibrium between the degrees of freedom corresponding to particle translation, electron excitation, and ionization can be accepted, at least for the inner zone of the plasma jet. To the contrary, the data for the absolute emission coefficient of N₂⁺ molecular band lines show that the degree of dissociation in the plasma jet is much in excess of that corresponding to equilibrium. This phenomenon can be explained as a result of the rapid temperature decay in the plasma from initially 13000 K in the arc heating zone to T ≦ 9000 K in the plasma jet zone proceeding in a time interval of 10^?5 s which is much shorter than the time necessary for adjustment of dissociation equilibrium. In the outer cool zone of the plasma jet, an unusual high intensity of the N₂⁺ radiation was found thus indicating the existence of a nonequilibrium excitation mechanism typical for a decaying nitrogen plasma. From the supernormal high degree of dissociation in the high-speed subatmospheric nitrogen plasma jet, conclusions are drawn with respect to its applicability as source of reactive particles in plasma-chemical experiments.     

Collisional broadening and line intensities in the ν2 and ν4 bands of PH3

Using a tunable diode-laser spectrometer self-broadening coefficients and absolute intensities have been measured for 26 lines of PH₃ at 298 K in the QR branch of the ν₂ band and the PP and RP branches of the ν₄ band. The recorded lines with J values ranging from 2 to 14 and K from 0 to 11 are located in the spectral range 995-1093 cm⁻¹. Self-broadening coefficients have also been measured at 173.4 K for nine of these lines. The collisional widths and line strengths are obtained by fitting each spectral line with different theoretical profiles. The results obtained for the line intensities are in good agreement with recent measurements [J. Mol. Spectrosc. 215 (2002) 178]. The self-broadening coefficients are also calculated on the basis of a simple semiclassical model involving only the electrostatic interactions. A satisfactory agreement is obtained except for high J values or K values equal to J, for which the calculated results are notably underestimated. By comparing broadening coefficients at room and low temperatures, the temperature dependence of these broadenings has been determined both experimentally and theoretically.     

The absorption line profiles of H2O near 1.39 μm in binary mixtures with N2, O2, and H2 at low pressures

The absorption line profiles of water vapor in binary mixtures with diatomic molecules H₂, N₂, and O₂ have been recorded on a diode laser spectrometer. The profiles of several lines of the 101 band have been studied near 1.39 μm with a spectral resolution of 3 × 10^?4 cm^?1. The pressure of the binary mixtures was varied from 0 to 200 Torr. The experimental data obtained have been used to test the Voigt, Rautian-Sobel’man, and Galatry theoretical models of a spectral line profile. The coefficients of collisional narrowing have been determined from the results of the fitting.     

H2-broadening,shifting and mixing coefficients of the doublets in the ν2 and ν4 bands of PH3 at room temperature

The broadening, shifting and mixing coefficients of the doublet spectral lines in the ν₂ and ν₄ bands of PH₃ perturbed by H₂ have been determined at room temperature. Indeed, the collisional spectroscopic parameters: intensities, line widths, line shifts and line mixing parameters, are all grouped together in the collisional relaxation matrix. To analyse the collisional process and physical effects on spectra of phosphine (PH₃), we have used the measurements carried out using a tunable diode-laser spectrometer in the ν₂ and ν₄ bands of PH₃ perturbed by hydrogen (H₂) at room temperature. The recorded spectra are fitted by the Voigt profile and the speed-dependent uncorrelated hard collision model of Rautian and Sobelman. These profiles are developed in the studies of isolated lines and are modified to account for the line mixing effects in the overlapping lines. The line widths, line shifts and line mixing parameters are given for six A₁ and A₂ doublet lines with quantum numbers K = 3n,?(n = 1,?2, …) and overlapped by collisional broadening at pressures of less than 50 mbar.     

Spectral Line HeII 6560 Å as a Sensor of the Electron Concentration in a Dense Plasma of a Current Sheet

Stark broadening of the spectral line HeII 6560 Å by plasma was studied. The profiles of the line HeII 6560 Å were calculated for different values of the electron concentration N_e. We used the quasi‐static approximation to account for the perturbing ions and the impact approximation to describe the perturbing electrons. The electron concentration N_e in the central region of a current sheet plasma was deduced by comparing the experimentally obtained profiles of the line HeII 6560 Å with the set of the theoretically calculated profiles of this line.