The n=2-1 spectral emission pattern of heliumlike argon, together with the associated satellite emission originating from lithiumlike argon have been measured with high-resolution x-ray spectroscopy at the Berlin electron-beam ion trap. The observed line intensity across a wide range of excitation energies was weighted by an electron-energy distribution to analyze as a function of plasma temperature the line ratios between KLL dielectronic recombination satellites, in particular the j+z, j, and k satellites, and the w-resonance line. A good agreement between various theoretical models is found, supporting the method of line-ratio measurement as a temperature diagnostic for plasmas. A value for the so-called R-line ratio is determined and calculations with the HULLAC suite of codes predict it to be electron density independent over a wide range.

Spectroscopy of heliumlike argon resonance and satellite lines for plasma temperature diagnostics.

The wavelengths of the 1s2s2p-1s22s and 1s2p2-1s22p transitions in Ar15+ have been measured using a crystal spectrometer and an electron beam ion trap. These spectral lines are satellites to the n = 2 resonance lines of He-like Ar16+ and play an important diagnostic role in high-temperature plasmas directed toward fusion research. The results of these measurements are compared with a number of different theoretical results, demonstrating the relative accuracy of these theoretical approaches.

http://iopscience.iop.org/article/10.1088/0953-4075/34/20/309/pdf

Wavelength measurements of the satellite transitions to the n = 2 resonance lines of helium-like argon

The abundance of potassium is derived from X-ray lines observed during flares by the RESIK instrument on the solar mission CORONAS-F between 3.53 A and 3.57 A. The lines include those emitted by He-like K and Li-like K dielectronic satellites, which have been synthesized using the CHIANTI atomic code and newly calculated atomic data. There is good agreement between observed and synthesized spectra, and the theoretical behavior of the spectra with varying temperature estimated from the ratio of the two GOES channels is correctly predicted. The observed fluxes of the He-like K resonance line per unit emission measure give log A(K) = 5.86 (on a scale log A(H) = 12), with a total range of a factor 2.9. This is higher than photospheric abundance estimates by a factor 5.5, a slightly greater enhancement than for other elements with first ionization potential (FIP) less than ~10 eV. There is, then, the possibility that enrichment of low-FIP elements in coronal plasmas depends weakly on the value of the FIP which for K is extremely low (4.34 eV). Our work also suggests that fractionation of elements to form the FIP effect occurs in the low chromosphere rather than higher up, as in some models.

/pdf/highly-ionized-potassium-lines-in-solar-x-ray-spectra-and-57l9264tgf.pdf

Highly ionized potassium lines in solar x-ray spectra and the abundance of potassium

A self-consistent method for the determination of neutral density from X-ray impurity spectra

Observations of He-like and H-like Ar (Ar XVII and Ar XVIII) lines at 3.949 Angstroms and 3.733 Angstroms respectively with the RESIK X-ray spectrometer on the CORONAS-F spacecraft, together with temperatures and emission measures from the two channels of GOES, have been analyzed to obtain the abundance of Ar in flare plasmas in the solar corona. The line fluxes per unit emission measure show a temperature dependence like that predicted from theory, and lead to spectroscopically determined values for the absolute Ar abundance, A(Ar) = 6.44 pm 0.07 (Ar XVII) and 6.49 pm 0.16 (Ar XVIII) which are in agreement to within uncertainties. The weighted mean is 6.45 pm 0.06, which is between two recent compilations of the solar Ar abundance and suggest that the photospheric and coronal abundances of Ar are very similar.

A solar spectroscopic absolute abundance of argon from RESIK

Calculations of excitation rates in Ar+16 and of nearby dielectronic satellite lines have been used to synthesize X‐ray spectra in the range 3.9–4.1 A where lines due to the chief n=1–2 transitions occur. These show excellent agreement with high‐resolution spectra obtained with the Alcator C tokamak.

Calculated ar-xvii line-intensities and comparison with spectra from the alcator-c tokamak

Using calculations of collisional excitation rates in He-like argon (Ar XVII) and intensity factors and other data for nearby dielectronic satellites, X-ray line spectra have been synthesized as a function of electron temperature and density The Ar XVII excitation rates were obtained from interpolations of R-matrix calculations, and are likely to be the best available at present The resulting spectra are compared with spectra observed from high-temperature plasmas in the Alcator C tokamak The agreement between observed spectra and those calculated using measured values of temperature and density illustrates the accuracy of the calculations, though there are small discrepancies which are likely to be connected with wavelengths or intensity factors for the Ar XVI satellites Thus, argon X-ray line spectra can serve as a means of diagnosing low-density, astrophysical (in particular solar-flare) plasmas for which there is no independent means of measuring temperatures

Calculated Ar XVII line intensities and comparison with spectra from the Alcator C tokamak

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Calculated ar-xvii line-intensities and comparison with spectra from the alcator-c tokamak

Calculated Ar XVII line intensities and comparison with spectra from the Alcator C tokamak