Measurement of width and shift of rare gas lines emitted from a stock-tube plasma

In a diaphragm shock-tube, Ar, Kr and Xe plasmas were generated with equilibrium temperatures of 8,000 to 12,000 K. The electron densities were measured with a two-wavelength interferometer and varied from 4×10¹⁶ to 1.4×10¹⁷ cm^-3. Emission profiles of spectral lines were recorded with a polychromator setup in 1 μs intervals using a fast data acquisition system. Width w and shift d turned out to be proportional to electron density N_e for the observed lines. Stark broadening parameters w/N_e and d/N_e are presented for 3 Ar(I), 4 Kr(I) and 5 Xe(I) lines in the visible region of the spectrum.     

Effects of radiator motion on plasma-broadened hydrogen lyman-β

For the hydrogen line L-β, broadening in an Ar⁺-plasma (N_e = 7.2 × 10¹⁶ cm^?3, T = 12,200 K) has been investigated with the help of a computer simulation of ion broadening taking full account of radiator motion. The anisotropy in Stark broadening for a moving radiator is found to be negligible under these conditions, but Stark profiles depend markedly on the radiator speed. The final line profile (including Stark and Doppler broadening) is nearly the same as the profile obtained by convolution of the Doppler profile with the Stark profile for radiators at rest and fictitious ions with the reduced mass of the atom-ion pair.     

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.     

Kinetic temperature and electron density measurement in?an?inductively coupled plasma torch using degenerate four-wave mixing

Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively coupled plasma. Measurements are performed in a 1 kW, 27 MHz radio-frequency plasma using a continuous-wave, tunable 811.5 nm diode laser to excite the 4s³P₂→4p³D₃ argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000±150 K. Electron densities measured range from 6.1 (±0.3)×10¹⁵ cm⁻³ to 10.1 (±0.3)×10¹⁵ cm⁻³. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. The Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.     

Experimental Stark broadening studies of the CI transition 3s1P1o ? 3p1S0 at 833.5 nm

Experimental Stark broadening studies of the infrared CI transition 3s ¹ P ₁ ^o − 3p ¹ S ₀ at 833.5 nm are reported for the first time. A high-current wall-stabilized arc, operated in a mixture of helium, argon, carbon dioxide and hydrogen, was applied as the plasma source. Radiation emitted from homogeneous and optically thin plasma layers was analyzed. Stark broadening studies of the selected CI transition and the hydrogen Balmer β line were performed. As expected from theoretical considerations, the CI line width depends linearly on the electron density of the plasma. Applying theoretical Stark broadening data for the H _gb line, the measured Stark widths of the CI line were calibrated for the purpose of electron density determination in low temperature plasmas.     

Atomic Model Calculations of Gain Saturation in the 46.9 nm Line of Ne‐like Ar

The gain saturation in the 46.9 nm line of the Ar⁺⁸ laser is analyzed using an atomic kinetics code. The dependence of the gain (G) on the electron kinetic temperature (T_e) in the region (50 ‐150 eV) is calculated in the quasi steady‐state approximation for the different values of the electron density (N_e) and the plasma radius (r_pl). The influence of radiat on trapping, ion random and mean velocities, Stark line broadening and refraction losses on the gain saturation is taken into consideration. For r_pl = 150‐600 μm, the amplplication (G > 0 cm^‐1) exists in the large temperature/density domain (T_e = 60‐150 eV, N_e = 0.5‐10 × 10¹⁸ cm^‐3). However, the value G_s ∼ 1.4 cm^‐1 required for the gain saturation at the typical plasma length L_pl ∼ 15 cm is reached in the extremely narrow density regions at the high temperatures. The saturation is reached for r_pl = 600 μm at T^s_e = 150 eV in the region N^s_e = 1.8‐2 × 10¹⁸ cm ^‐3, for r_pl = 300 μm at T^s_e = 125 eV and N^s_e = 2.5‐3 × 10¹⁸ cm^‐3, and for r_pl = 150 μm at T^s_e = 110 eV and N^s_e = 3‐4 × 10¹⁸ cm^‐3. The broadest density region (N^s_e = 2 ‐8 × 10¹⁸ cm^‐3) is predicted for the narrowest column (r_pl = 150 μm) at the highest temperature (T^s_e = 150 eV). The operation in the broadest density region N^s_e, should make easier achievement of the gain saturation in the experiments.     

Stark broadening and displacement of isolated He I lines

Experimental results for Stark broadened He I lines emitted by a helium plasma jet (N_e≈3×10¹⁶ cm^-3) are compared with theory; agreement is well enough for widths whereas shifts calculations present generally large discrepancies with experimental data.     

Distribution of deep levels in Si:Au by spectral analysis of deep-level transient spectroscopy

-l eV and Δσ=1.4×10^-15 cm²) around their mean values (E₀=0.47 eV and σ₀=5.0×10^-15 cm²). No broadening for the other levels is observed in the emission rate spectrum. Accepted: 13 October 1997     

Theψ-particles in an SU4 scheme with anomalous currents

The recently discovered narrow peaks (theψ-particles) in e⁺e⁻ system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU₄ symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU₃ quantum numbers in the group SU₄. Theψ (3.1) is assigned to a near ideally mixed15⊕1 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed15⊕1 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can changeZ. The decays of theψ-particles are discussed. New enlarged SU₄ multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation of two rather broad resonances in e⁺ e⁻ collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays of theψ-particles. Important results concerning the recently observed phenomena in the process e⁺e⁻→hadrons follow in this scheme.     

大气压等离子体炬电子密度的光谱诊断

利用空心针-板放电装置产生了大气压等离子体炬,采用光谱法测量了其内部及表面的电子密度. 向空心针中通入氩气,在大气环境中产生了长度为1cm的等离子体炬.实验分别测量了Hα谱线和ArⅠ(696.54nm)谱线,通过反卷积方法分离出其相应的Stark展宽,并由此计算了电子密度.结果发现,采用Hα谱线和ArⅠ(696.54nm)谱线Stark展宽计算得到的等离子体的电子密度分别为1.0×10¹⁵cm^－3和3.78×10^{15关键词： 等离子体炬 电子密度 气体温度 Stark展宽}     

Re-appraisal of the <Emphasis Type="Italic">P,T</Emphasis>-odd interaction constant <Emphasis Type="Italic">W</Emphasis><Subscript>d</Subscript> in YbF: Relativistic configuration interaction approach

Restricted active space (RAS) configuration interaction (CI) approach is employed to compute the P,T-odd interaction constant W _d for the ground (²Σ_1/2) state of YbF molecule. The present estimate of W _d = −1.164 × 10²⁵ Hz/e-cm is expected to provide a reliable limit on the electron’s electric dipole moment (EDM), d _e.     

Crystal-field splitting of Pr<Superscript>3+</Superscript> ion multiplets in YPO<Subscript>4</Subscript> with allowance for interconfigurational interaction

The crystal-field splitting of the Pr³⁺ ion multiplets is analyzed with regard to the influence of excited opposite-parity configurations 4f ^{(N − 1)}5d and a configuration with charge transfer. Such an approach makes it possible to (i) refine the characterization of the Stark structure of multiplets by 39% compared with the approximation of a weak configurational interaction and (ii) determine the covalence parameters and the parameters of an odd-symmetry crystal field from experimental data for the Stark structure. The covalence parameters thus determined coincide in order of magnitude with the respective parameters calculated for other ligands using microscopic models.     

Theoretical studies on dielectronic recombination of neonlike gold and its effects on plasma ionization balance and radiation energy

The dielectronic recombination (DR) of neonlike gold ions is investigated employing the flexible atomic code based on the relativistic configuration interaction method, and its influence on the ionization balance and radiation energy in high-temperature plasma is also studied. The total resonance strength for LMM configuration complex is in a good agreement with the experimental measurement and other theoretical works. The DR rate coefficients are calculated and compared with the three-body recombination and radiative recombination rate coefficients. The DR process is the dominant recombination mechanism of Ne-like gold ions for plasma with temperature T_e≥6.5 keV and density n_e≤2×10²² cm^-3, which is close to the condition of X-ray conversion region in the inertial confinement fusion. Moreover, the DR satellite spectra of LMM, LMN and LMO resonances are simulated, and compared with the intensities of the corresponding resonance lines induced by the electron impact excitation. The intensity ratio of the satellite line 3D’ [(2p⁵_3/23d_3/23d_5/2)_J=5/2[(2p^{5}_{3/2}3d_{3/2}3d_{5/2})_{J=5/2}–(2p⁶3d_3/2) _J=3/2](2p^{6}3d_{3/2})_{ J=3/2}] and the resonance line 3D [(2p⁵_3/23d_5/2)_J=1[(2p^{5}_{3/2}3d_{5/2})_{J=1}–(2p⁶)_J=0](2p^{6})_{J=0}] is given, which can be applied for diagnostics of plasma temperature.     

Comparison between single- and double-pulse LIBS at different air pressures on silicon target

A comparative study between single- and double-pulse laser-induced breakdown spectroscopy (LIBS) was performed on an n-type silicon(111) target. A new mobile double-pulse instrument for LIBS analysis was used for the measurements. The experiment was carried out at different air pressures of 0.7, 470 and 1000 hPa. It has been found that, in the case of double-pulse LIBS, the emission intensities of atomic and ionic lines are strongly enhanced at higher pressures. Using Stark broadening of the atomic lines of silicon, it was found that the electron number densities for single and double pulses are approximately the same (N_e∼10¹⁷ cm^-3). Plasma excitation and ionization temperatures were determined from a Boltzmann plot. The double-pulse laser-induced plasma was studied at different interpulse delay times of 1, 2, 5, 10, 15, 25 and 50 μs. The results indicated that the interaction between the laser, plasma and target gives higher atomic and ionic intensities at shorter interpulse delay times. PACS 52.38.Mf; 79.20.Ds; 52.50.Jm     

Experimental studies of few-body systems at MAMI

Few-body experiments at the Mainz Microtron were focused on a number of selected topics. Double-polarization experiments to determine the neutron electric form factor G_en have been performed using both deuterium and polarized helium-3 targets. The structure of ³He has been studied in the reactions ³H e⃗ e(e⃗e,e′n) and ³H e⃗ e(e⃗e,e′p) with large (transversal) missing momenta and in quasi-elastic electron scattering. Electromagnetically induced two-nucleon knockout has been investigated in order to study the role of correlated nucleon-nucleon motion in the nucleus. Measurements of the (e,e′pn) reaction on ³He and ¹⁶O were performed for the first time. A triple-polarization experiment of type ³H e⃗ e(e⃗e,e′e⃗p⃗)d has been performed, where, in addition, the spin of the knocked out proton is analyzed. This measurement provides information on the spin-dependent momentum distribution of proton-deuteron clusters in the ³He nucleus. Hence, by tagging the outgoing deuteron spin-polarized ³He might also serve as an effective polarized proton target for electron scattering experiments. Moreover, in inclusive ^3,4He(e,e′) measurements at low momentum transfer, the effect of 3-body-forces has been studied.     

SiH4激光等离子体内H谱线的线型研究

本工作利用光学多道分析仪(OMA Ⅲ)测量了脉冲TEA CO₂激光诱发的SiH₄等离子体内H Balmer系的H_α,H_σ和H_γ线的线型。结果表明,三条谱线的FWHM(半值全宽度)随跃迁上能级的主量子数的增加而增加,即△λ_1/2(H_α)<△λ_1/2(H_β)<△λ_1/2(H_γ)。通过对等离子体内各类加宽机制的讨论,得出等离子体内谱线的主要加宽机制为Stark加宽。由H_α线的实验线型与Stark加宽理论线型的拟合,得到等离子体的两个重要参量,平均电子密度N≈10¹⁷cm^-3,电子温度T≈40 000K。由H_β线的时间分辨测量得到等离子体的电子密度随时间的演变曲线。 关键词：     

Measurement of electric field strengths in a waveguide by means of the dynamic Stark effect in hydrogen and neutral helium spectral lines

The dynamic Stark effect of the spectral lines H_β and of the neutral helium lines λ=402.6 nm (2³ P ⁰−5³ D) and λ=438.8 nm (2¹ P ⁰−5¹ D) emitted from a discharge tube was used for probing rf electric fields in a transverse waveguide. Calculations accounting for the pertubation of the atomic states by strong unidirectional fields prove to be suitable in order to interprete the main experimental results. If the waveguide is terminated with a metallic reflector and the plasma in the discharge tube becomes overdense—then representing a slightly permeable mirror—a resonant enhancement of the electric field strength may be achieved by tuning. This enhancement is well recognizable in the spectral line contours.     

Stark broadening of the hydrogen Paschen <Emphasis Type="Bold">γ</Emphasis> transition at electron densities of the order of cm

Stark broadening measurements and calculations of the Paschen γ spectral line of hydrogen ( λ = 1.094[: MU :] m) are reported. Investigations have been performed at plasma electron densities between 1.4×10 ¹⁵ cm ^-3 and 3.7×10 ¹⁵ cm ^-3 . As the light source a wall-stabilized arc operated in a helium-hydrogen gas mixture at atmospheric pressure has been applied. The radiation of the plasma emitted from nearly homogeneous plasma layers in end-on direction, was measured with the use of a grating spectrometer equipped with a charge coupled device (CCD) detector. The radiance calibration was carried out against light outputs originating from a tungsten strip radiation standard. The measured FWHM are compared with results of our calculations based on computer simulation techniques (full computer simulation method -- FCSM). Our broadening data are also compared with results of other theoretical approaches (MM-method, quasi-static approximation) and with experimental data obtained at electron densities about one order of magnitude larger than ours. Received 21 January 2003 Published online 24 April 2003 RID="a" ID="a"e-mail: wujec@uni.opole.pl     

Laser induced breakdown spectroscopy of germane plasma induced by IR CO2 pulsed laser

Laser-induced breakdown spectroscopy (LIBS) in germane (GeH₄), initially at room temperature and pressures ranging from 2 to 10 kPa, was studied using a high-power transverse excitation atmospheric (TEA) CO₂ laser (λ=10.653 μm, τ _FWHM=64 ns and power densities ranging from 0.28 to 5.52 GW cm⁻²). The strong emission spectrum of the generated plasma is mainly due to electronic relaxation of excited Ge, H and ionic fragments Ge⁺, Ge²⁺ and Ge³⁺. The weak emission is due to molecular bands of H₂. Excitation temperatures of 8100±300 K and 23,500±2500 K were estimated by Ge atomic and Ge⁺ singly ionized lines, respectively. Electron number densities of the order of (0.7–6.2)×10¹⁷ cm⁻³ were deduced from the Stark broadening of several atomic Ge lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the germane pressure and laser irradiance. Optical breakdown threshold intensities in germane at 10.653 μm have been determined. The mechanism of initiation of the laser-induced plasma in germane has been analyzed.