Fig 5 - uploaded by Konstantin Tsigutkin
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Determination of the Doppler broadening using the 2p-3d line shape measured at a distance of 5 mm from the target. The instrumental function is displayed by the dashed line, and the dot-dashed curve corresponds to the Doppler broadening.
Source publication
An accurate knowledge of the Li i 4d–4f energy separation is essential for the determination of electric fields, as is pursued using several modern diagnostic techniques. However, there is a rather large spread in the values of this quantity in the available data sources. We have measured the Li i 4d–4f energy separation using a technique that comb...
Contexts in source publication
Context 1
... less sensitive to the Stark broadening than the 2p-4d transition, and its width, for plasma densities below 10 14 cm −3 , is only affected by the Doppler effect. Therefore, the Doppler broadening can be obtained from the 2p-3d profile by deconvolving the instrumental function from the total line shape. The 2p-3d line profile is presented in Fig. 5. The instrumental function is that shown in Fig. 4, scaled based on the spectrometer dispersion (0.083 Å/pixel) at this wavelength. Note that no assumption on the form of the Doppler broadening was made except for being a symmetric function. The convolution of the two broadening functions is given by the solid line, and the ...
Context 2
... the instrumental and Doppler broadening at hand we can proceed to the line-wavelength analysis. The measured broadening functions are deconvolved from the total experimental line shape of the 2p-4d transition in order to obtain the small Stark contribution. The Doppler broadening functions are those from Fig. 5, scaled by the 2p−4d / 2p−3d factor. The resulting calculated line shapes are presented in Fig. 6. On the plot, all mechanisms (instrumental, Doppler, and Stark broadenings) contributing to the line shape are shown independently. The wavelength difference between the 2p-4d and 2p-4f transitions is accurately determined from the Stark ...
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... For degenerate or nearly-degenerate atomic systems such as hydrogen-like atoms or Rydberg states, this condition is usually satisfied. This is also true for the Li I460 nm line, the Stark broadening of which is largely determined by the 4d-4f dipole interaction, with the two levels separated by only 0.6 meV » [32], orders of magnitude smaller than the electron temperatures inferred in the present study, k T 1 2 eV e B~-. Therefore, for the plasma conditions typical for the current study, the Stark broadening of this line is described by the semiclassical CS model very accurately. ...
We present results of experimental and theoretical studies of the Stark broadening of the Li i 460 nm spectral line with forbidden components and of the isolated 497 nm line. Plasma was induced by Nd:YAG laser radiation at 1064 nm with pulse duration ∼4.5 ns. Laser-induced plasma was generated in front of the alumina pellet, with some content of Li2CO3, placed in a vacuum chamber filled with argon under reduced pressure. Plasma diagnostics was performed using the laser Thomson scattering technique, free from assumptions about the plasma equilibrium state and its composition and so independently of plasma emission spectra. Spatially resolved spectra with Li lines were obtained from the measured, laterally integrated ones applying the inverse Abel transform. The Stark profiles were calculated by computer simulation method assuming a plasma in the local thermodynamic equilibrium. Calculations were performed for experimentally-inferred electron densities and temperatures, from 1.422 ×10²³ to 3.55 ×10²² m⁻³ and from 1.96 eV to 1.04 eV, respectively. Our studies show very good agreement between experimental Stark profiles and those computer simulated.
... In general, NIST atomic data [31] were used for the present calculations. However, the crucially important for the Li I 460.28-nm line shape energy difference ΔE 4d,4f ≈ 6.8 cm −1 as inferred from the NIST database is believed to be wrong [32]. Therefore, we instead employed ΔE 4d,4f ≈ 5 cm −1 , derived consistently by recent theoretical studies [33,34]. ...
... The most obvious effect is the depression of energies for lower-l states, which arises from the polarization and penetration of the core by the Rydberg electron. For the Rydberg states of lithium, there are many experimental measurements reported in the literature [9][10][11][12][13][14][15], but there are few measurements on 1s 2 nf 2 F high Rydberg states. Baig et al [16] reported observations of the Rydberg states of atomic lithium excited by the two-colour three photon resonance ionization technique in conjunction with a space charge limited thermionic diode ion detector; the odd parity nf 2 F Rydberg series were detected for the first time for n = 13-48, only 50 cm −1 from the ionization limit. ...
... e Radziemski et al [13]. f Tsigutkin et al [14]. g NIST Atomic Spectra Database [9]. ...
... Radziemski et al [13] used low-current hollow cathode sources and Fourier-transform spectrometry to determine the 4d-4f energy splitting as (4.988 ± 0.003) cm −1 , without reflecting the accuracy in the field-free limit. Tsigutkin et al [14] measured the LiI 4d-4f energy separation using a technique that combines laser-induced-fluorescence with the utilization of collisional excitations; they evaluated the 4d-4f energy separation in the field-free limit as 5.1 ± 0.2 cm −1. Safronova et al [19] presented a calculation of the 4d-4f energy separation in Li I with relativistic all-order perturbation theory values of E(SD) = 4.99 cm −1 , E(SDpT) = 4.92 cm −1 and a multiconfiguration Hartree-Fock value of E(MCHF) = 4.98 cm −1. ...
Ionization potentials and quantum defects of 1s2nf bound states and their adjacent continuum states for the lithium atom are calculated with the R-matrix theory; then the quantum defect function (QDF) of the 1s2nf channel is obtained, which varies smoothly with the energy based on the quantum defect theory. The original QDF is calibrated from a more accurate literature value and used to calculate quantum defects, ionization potentials and term energies (relative to the 1s22s ground state) of 1s2nf high Rydberg states of the lithium atom. The term energies in this work are, on the whole, in good agreement with the experimental data in the literature.
... Therefore, the 4f–4d energy separation is crucial for an accurate modeling. We have measured its value independently [21] in order to resolve the ambiguity in light of the large spread in the values of this quantity in the available data sources. ...
... In this case the spatial resolution along the line of sight is determined by the width of the pumping laser beam, which is ≃ 1.5 mm, whereas the resolution in the plane perpendicular to the line of sight is chosen by the spectrometer slit dimension (sub-mm scale). A detailed discussion of the spectral calibration and the determination of the instrumental response of the system can be found in Ref. [21]. ...
... The figure shows the measured and simulated line shapes of the allowed 2p-4d and the nearby forbidden 2p-4f transitions. The line shape simulation, similar to that described in Ref. [21], show the individual contribution of each of the three broadening mechanisms: the Stark effect, Doppler, and instru- mental. The Doppler broadening can be estimated from the Li i velocities obtained from time-of-flight measurements. ...
Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spectroscopy and line-shape analysis. Plasma doping allows for three-dimensional spatially resolved measurements. The measured peak magnitude and propagation velocity of the electric field is found to match those of the Hall electric field, inferred from the magnetic-field front propagation measured previously.
We present a calculation of the 4d-4f energy separation in Li I using two advanced techniques in atomic structure theory, namely, the relativistic all-order method and the multiconfiguration Hartree-Fock (MCHF) method. The accuracy of our calculations was investigated by conducting a third-order many-body perturbation theory calculation that allowed us to evaluate the importance of fourth- and higher-order corrections. A large-scale MCHF calculation was performed using the active space method and the core-polarization approximation. The obtained results provide an important test of these methods against each other and are shown to agree with the most accurate available experimental data.
