Ar XVII Research Articles

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.

Helium-like Argon Line Emission in Solar Flares

view Abstract Citations (9) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Helium-like Argon Line Emission in Solar Flares Phillips, K. J. H. ; Harra, L. K. ; Keenan, F. P. ; Zarro, D. M. ; Wilson, M. Abstract Theoretical X-ray spectra of Ar XVII lines and Ar XVI satellites at ∼4 Å, derived from R-matrix code and other calculations, are compared with solar-flare observations obtained with the SMM Flat Crystal Spectrometer. There is good agreement between the observed line features and those in the theoretical spectra, and the comparison leads to best-fit values of electron temperature for the observed solar flares. We present wavelengths for the Ar XVII and some Ar XVI lines, measured from the observed spectra, which have better precision than previous values. In addition, the coronal Ar/S abundance is determined from the relative intensities of Ar XVII lines to those of nearby S XV transitions, and the value of this ratio is discussed in the light of previous work. Publication: The Astrophysical Journal Pub Date: December 1993 DOI: 10.1086/173495 Bibcode: 1993ApJ...419..426P Keywords: ATOMIC DATA; ATOMIC PROCESSES; SUN: ABUNDANCES; SUN: FLARES; SUN: X-RAYS; GAMMA RAYS full text sources ADS |

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

Using recent atomic calculations, X-ray Ar XVII line spectra have been synthesized as a function of electron temperature and density. These are compared with Alcator C tokamak spectra and show excellent agreement for measured values of temperature and density. Argon X-ray line ratios can thus serve as useful diagnostics of, e.g., solar plasmas for which direct measurements of temperature and density are not available.

Doubly excited states in lithiumlike Si XII, S XIV and Ar XVI

Doubly excited states in lithiumlike Si XII, S XIV and Ar XVI

Evaluation of hot spots parameters by simple soft x-ray diagnostics

Properties of the hot spots in Ar and Ne plasma of a gas-puff z-pinch were investigated. Pinhole cameras with entrance diameter 13–250 Μm, XRD, semiconductor detectors and flat crystal spectrographs with Si and KAP crystals were used for spatially, temporally and spectrally resolved soft x-ray diagnostics. The diameters of Ar (25–30 Μm) and Ne (40 uΜm) hot spots were found and K-shell x-ray spectra were registered. Temporal evolution of x-rays within ≈600 ns was observed; the upper estimate of hot spots lifetime did not exceed 50 ns. The described processing and curve fitting of He-like Ar XVII lines provided the values the of electron temperature and density in Ar hot spotsT e=1·0–1·1 keV,n e=(1·8–4·0)×1027 m−3, which support the idea of the Bennett equilibrium validity for the spots.

The Ar/Ca abundance ratio in solar flares

An Ar/Ca abundance ratio of at least 0.56 is derived using the X-ray spectra of solar flares recorded by the SOLFLEX spectrometers on the P78-1 spacecraft. The method involves determining the contribution of the Ar XVII 1s2 1S0-1s4p 1P1 line to a blended feature at 3.2005 A. This contribution is determined by considering the relationship of the other component of the blended feature, namely the Ca XVIII 1s2 2s 2S(1/2)-1s2p2s 2P(3/2) line, to the dielectronic satellite lines of Ca XVII that fall between 3.215 and 3.24 A. It is demonstrated that a broad-wavelength coverage solar X-ray spectrometer experiment is necessary for precise abundance measurements.

Measurement of wavelengths for inner-shell transitions in CA XVII-XIX

The wavelengths of transitions in solar flare spectra in the region 3.12-3.24 A have been measured using data recorded by a crystal spectrometer on the Air Force P78-1 spacecraft. Appearing in this wavelength region are inner-shell transitions of the type n = 1-2 in Ca XVII-XIX and resonance transitions in Ar XVII, Ar XVIII, and Fe XXV. The hydrogenic Ar XVIII 1s-1p transition was used to establish an absolute wavelength scale with an estimated uncertainty of 0.3 mA, and the relative wavelengths were measured to an uncertainty that is typically less than 0.1 mA. The presently measured wavelengths are compared with previously measured and calculated wavelengths, and the observed flare spectra are compared with synthetic spectra.

Extension of the theory for the intensities of dipole forbidden spectral lines in a plasma

A consistent theory describing the effect of appearance of dipole-forbidden spectral lines (FSL) in a plasma is developed. The theory accounts only for the contributions of quasi-static ions to the FSL intensity, the boundary between these ions andthe remaining ions being determined from a multiparticle description of the plasma microfield. The contribution of electrons has been treated in a standard manner. The present analysis has been performed for more complicated four-level schemes of the energetic spectrum of emitters than previous calculations by the authors. This result makes it possible to enlarge significantly the class of possible emitters and, therefore, of plasmas accessible to the corresponding diagnostic technique. The results obtained eliminate many of the discrepancies between theoretical and experimental values of the ratio of intensities of FSL ( I f) and ASL—allowed spectral lines ( I a). The effects of quadrupole interaction, caused by inhomogeneity of the disturbing microfield on the intensities of forbidden I f and corresponding allowed I a lines, have been analysed. It is shown that, in dense high-temperature plasmas, quadrupole interactions may dominate. Their contributions to I f and I a have been calculated analytically for the multi-particle description of the plasma microfield. As examples, we present calculated values of the ratio I f/ I a for the lines Ne IX 13.447 Å and Ar XVII 3.904 Å. Accounting for the quadrupole interaction is shown to change the I f I a ratios radically (by a factor of 2–3) in the range of concentrations N e = 10 21-3 x 10 24 cm -3 and temperatures T i = 0.25-4.5keV. The I f I a ratios have been tabulated for the lines He I 4471 Å, He I 4922 Å He I 6678 Å, C IV 1106.4 Å and Cu I 4016 Å, which can be efficiently used for measuring the electron concentration N e and the ion temperature T i in the range of N e = 10 15-10 18 cm -3 and T i = 1−100 eV.

Precision measurement of transition energies and Lamb shifts in two-electron argon and potassium in solar-flare spectra.

The wavelengths of $1{s}^{2}^{1}S_{0}\ensuremath{-}1\mathrm{snp}^{1}P_{1}$ transitions in the two-electron ions Ar xvii and K xvii have been measured in solar-flare spectra. The QED contributions to the transition energies are determined by comparison of the measured transition energies to the calculated values. The ionization limit of Ar xvii is also determined.

Recombination-cascade X-ray spectra of highly charged helium-like ions

It is shown that the relative intensity distribution among the X-ray spectral lines of helium-like ions from the n = 2 states produced through recombination processes such as radiative and charge transfer recombination may be given by considering in detail the radiative cascades following recombination. Model calculations are presented with predicted line ratios for Ar XVII and Fe XXV in recombination-dominated noncoronal plasmas. In particular, compared to coronal intensities, the singlet resonance line (w) should be much weaker relative to the triplet intercombination (x, y) and forbidden (z) lines, yielding large values for the ratio G = (x + y + z)/w. Accurate configuration interaction type wave functions are employed to calculate the eigenenergies, transition probabilities, and cascade coefficients. Certain relevant tokamak and astrophysical observations are discussed.

Digital enhancement of the argon dielectronic satellite spectrum from a laser-imploded microballoon

The spectral resolution of the argon dielectronic satellite radiation from the core plasma of a laser-imploded microballoon is improved by digital processing. The instrumental profile of the crystal spectrograph is deconvolved from the data, and four satellite features appear on the long wavelength side of the Ar XVIII Lyman-alpha line in the resulting enhanced spectrum. The transitions from the 2s2p 3P and 2p 2 3P doubly excited levels of Ar XVII are identified. These satellite transitions are useful as a density diagnostic for the microballoon core plasma.

Inner-shell excitation of argon dielectronic satellite spectral lines in imploded microballoon plasmas

The dielectronic satellite transitions, originating on the 2s2p 3P and 2p2 3P doubly excited levels of helium-like Ar XVII, are identified in the spectrum from the laser-imploded core plasma of an argon filled glass microballoon. The intensities of these transitions are consistent with inner-shell excitation from the AR XVII 1s2s 3S and 1s2p 3P metastable levels. This implies that the Ar XVII ionisation stage is overheated and is undergoing transient ionisation in the core plasma.

Series Formulae for the He I-like Spectra Na X through Ar XVII (Z=11-18)

The constants in Rydberg-Ritz formulae have been evaluated for 1snl series by fitting the lowest few terms. Each formula allows prediction of the energies of all terms of a particular type in a particular spectrum. Formulae are given for the 3S1, 1S0, 3P00, 3P10, 3P20, 1P10, 3D1,2, 3D3, 1D2, and 1,3F0 series in each spectrum. The formulae for the S and P0 series are based on values of the lower terms calculated by Ermolaev and Jones, and thus effectively extend these calculations to all series members. Values of the 1s4d and 1s5d terms needed for derivation of the D formulae were obtained by procedures based on comparisons and use of several different calculations of the 1s3d levels. The results for the higher D terms should be more accurate than previous values calculated without inclusion of the relativistic effects. Similar procedures were used in the derivation of the 1snf formulae. The 1snl term values for l ≧ 4 should be equal to the appropriate (relativistic) hydrogenic values to a good accuracy for these ions. The wavelengths of all transitions of the type 1snl-1sn'l' can thus be predicted for these spectra. The predicted and experimental results for some 1s2-1snp and 1s2s 3S-1s2p 3P0 transitions are compared.

X-ray spectra from a gas-puff z-pinch device

X-ray emission was used to diagnose the plasma formation in a gas-puff pulsed-discharge device. X-ray pinhole images were collected simultaneously with x-ray spectra from Ar and Kr gases. X rays were emitted from z-pinched regions (50–100 μm in diameter) along a collinear track formed by the plasma implosion of a hollow gas jet. Spectral analysis indicated Ar plasma formation with electron densities of ∼2×1021 cm−3. The Ar plasma temperature was ∼1 keV, based on a collisional-radiative transport model. Li-like satellite lines were classified in Ar XVI with atomic structure calculations. The Kr x-ray spectrum (6–8-Å region) was dominated by Ne-like Kr XXVII lines. New spectral transitions were classified in Na-like Kr XXVI and F-like Kr XXVIII. The wavelength calibrations in the Kr spectrum were obtained from exploded-Al-wire plasma generated in coincidence with the plasma implosion formed in the puff gas.

Doppler-tuned beam-foil X-ray spectrometer

A new type of X-ray spectrometer for use with fast foil-excited beams has been devised and tested. The spectrometer operates by matching the Doppler-shifted emission from the beam with a known absorption feature (such as a K-edge) in a thin filter between the source and the detector. Tuning is accomplished by varying the angle between the detector and the beam. Knowledge of the angle, beam velocity and the filter absorption profile is sufficient to determine the emission spectrum of the beam source. Resolving powers of 10 3 to 10 5 are expected. A prototype device has been constructed and tested at the Berkeley HILAC. In initial experiments, the energy of the 2 1P 1−1 1S 0 transition of heliumlike argon (Ar XVI) was measured by bringing the emission from the 412 MeV Ar beam into coincidence with the L III absorption edge of Ag near 3.36 keV. The principle of this spectrometer can be extended to other spectral ranges, and it should be useful for both survey and high-precision measurements

Rocket Observation of AR Xii-Xvi CA Xiv-Xviii and fe XIV, xv, XXIV in the Extreme-Ultraviolet Spectrum of a Solar Flare

view Abstract Citations (48) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rocket Observation of Ar XII-XVI Ca XIV-XVIII and Fe XIV, XV, XXIV in the Extreme-Ultraviolet Spectrum of a Solar Flare Purcell, J. D. ; Widing, K. G. Abstract The lithiumlike doublets of S xiv, Ar XVI, and Ca xviii are identified in the 300-450 A region by extrapolation of solar wavelengths and term intervals in the isoelectronic sequence. A possible observation of Fe xxiv in the flare is discussed. The solar blend at 417 A involving S xiv and the Fe xv inter- system line is resolved. The singlet resonance lines of S xiii, Ar xv, and Ca xvii are also found in the flare spectrum by isoelectronic extrapolation. Ca xiv and Ca xv are identified on the basis of laboratory wavelengths. The problem of the identification of boron-like Ar xiv and Ca xvi is discussed. The weakness of argon lines relative to calcium lines in the flare is consistent with a solar abundance of argon less than calcium. An electron density of 3 >( 1010 in the flare core is estimated from the intensity ratio of the Fe xiv lines at 211 and 219 A. Publication: The Astrophysical Journal Pub Date: August 1972 DOI: 10.1086/151626 Bibcode: 1972ApJ...176..239P full text sources ADS |

Theory of Relativistic Magnetic Dipole Transitions: Lifetime of the Metastable2S3State of the Heliumlike Ions

It has recently been established that the radiative lifetime of the metastable $2^{3}S$ state of helium and the heliumlike ions is determined by single-photon magnetic dipole ($M1$) transitions to the ground state, rather than the two-photon process proposed by Breit and Teller. The theory of $nl\ensuremath{-}{n}^{\ensuremath{'}}l$ $M1$ transitions with $n\ensuremath{\ne}{n}^{\ensuremath{'}}$ is developed in the Pauli approximation and extended to two-electron systems. Terms arising from relativistic energy corrections and finite-wavelength effects are included. The results for hydrogenic systems are shown to be identical to those obtained in the relativistic four-component Dirac formulation. The coefficients in the ${Z}^{\ensuremath{-}1}$ perturbation expansion of the $1s2s^{3}S\ensuremath{-}1{s}^{2}^{1}S$ $M1$ transition integral are evaluated through ninth order and used to calculate the $M1$ emission probabilities from the $2^{3}S$ state of the two-electron ions up to Fe XXV. The emission probability for neutral helium is 1.27 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ ${\mathrm{sec}}^{\ensuremath{-}1}$. The results are compared with recent solar coronal observations by Gabriel and Jordan, and with a measurement of the $2^{3}S$ state lifetime in Ar XVII by Schmieder and Marrus.

Relativistic Magnetic Dipole Emission: Lifetime of the1s2sS13State of Heliumlike Argon

The lifetime of the $1s2s^{3}S_{1}$ state of the heliumlike atom Ar XVII has been measured by observing the decay in flight of the metastable component of a fast foil-excited beam. The decay occurs predominantly by relativistic magnetic-dipole emission, a process first discussed by Breit and Teller. The result, $\ensuremath{\tau}(2^{3}S_{1})=(172\ifmmode\pm\else\textpm\fi{}30)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec, is compared with a recent calculation by Drake of the $M1$ transition probability.

Observation of the magnetic-dipole decay of the 2 3S 1 state of helium-like Si XIII, S XV, and Ar XVII

The observation in a laboratory experiment of the magnetic-dipole decay 2 3S 1-1 1S 0 in the helium-like atoms Si XIII, S XV, and Ar XVII is reported.

Spectra of highly ionized neon and argon in a plasma focus discharge

Valency-electron transitions with up to 4 kev energy in highly stripped ions are produced in the transient pinch which occurs in a coaxial plasma gun `Plasma Focus'. New or improved wavelengths for transitions in H-like and He-like neon and argon ions are measured and are identified by comparison with Hartree-Fock (HX) calculations of atomic structure made by Cowan in 1966 and 1968. Observed wavelengths of the He-like resonance lines lead to extrapolated values for the ionization potentials of Ar XVII and Ne IX. Inner-shell transitions in less highly stripped ions are also identified.