P. Mandelbaum

The potential for plasma diagnostics from stellar extreme-ultraviolet observations

A description of the lines from the most abundant ions in the EUV spectrum in the range 50-500 A that have special diagnostic significance is presented. These lines are from plasmas in the temperature range from 10 exp 5 to 10 exp 7 K. Their utility for determining temperature, density, and abundances is demonstrated. An objective grating spectrometer, based on the Skylab slitless spectrograph, for making celestial observations in the EUV spectral region with high spectral resolution is also described. Such an instrument, if equipped with a multilayer grating, can achieve efficiencies over limited EUV wavelength ranges that rival much larger telescope-spectrometer instruments for the observation of stars and other celestial objects.

Quenching of transition arrays through configuration mixing

In the atomic central-field model, the cancellation of some electric-dipole line strengths is a well known effect of configuration mixings. The authors study their global effects on transition arrays. A crucial quantity is the wavenumber mu 1 of the centre of gravity of two transition arrays when their upper or lower configurations mix. A closed formula is derived for the difference delta Emix between the values of mu 1 with and without the mixing effects. Two experimental examples are presented. In the first one, the value of delta Emix is a sufficient proof that one of the two arrays is almost completely quenched by the other. In the second one, the quenching is only partial, and the degree of quenching is evaluated. In conclusion using the unresolved transition array (UTA) formalism, it is possible to determine ab initio the centre of gravity of a mixed array, without any need for diagonalisation, and to deduce the main effects of configuration mixing.

Classification of X-Ray Spectra from Laser Produced Plasmas of Atoms from Tm to Pt in the Range 6-9 Å

X-ray spectra of highly ionized tungsten and neighbouring atoms (Tm, Yb, Hf, Ta, W, Re and Pt) has been observed from laser produced plasmas in the λ = 6-9 A range. Beside the prominent lines of the Ni I-like ions, lines belonging to Co I (3d9-3d84p), Cu I (3d104s-3d94s4p, 3d104p-3d94p2) and Zn I-like ions (3d104s2-3d94s24p, 3d104s4p-3d94s4p2) have been identified. Classification was based on isoelectronic sequence analysis and on comparison with ab-initio relativistic calculations. A collisional-radiative model of the Cu I-like ions in the plasma is used to show that the contribution of the 3d104d-3d94p4d and 3d104f-3d94f4p transition arrays to the 3d-4p spectrum is small. The importance of configuration interaction is pointed out. Computations agree with measurements within experimental uncertainty.

The Unresolved 3d-4f Transitions in the X-ray Spectra of Highly Ionized Tm to Re from Laser Produced Plasma

The broad, characteristic, pseudo-continua appearing in many spectra of highly ionized heavy atoms (5-8 A) are interpreted as superpositions of Spin-Orbit-Split Arrays, a particular case of Unresolved Transition Arrays for which formulas have been published recently. They pertain to 3d-4f transitions in atoms isoelectronic to Cu, Zn, Ga and Ge. Some individual lines belonging to the Co sequence are also identified. Effects of departure from pure jj coupling are discussed.

Nickel-like spectra of elements Y xii to Ag xx from a vacuum spark

The spectra of elements Y, Zr, Nb, Mo, Ru, Rh, Pd, and Ag in the 10–100-A range were obtained from a high-power vacuum spark and a grazing-incidence high-resolution spectrograph. The transitions 3d10–3d94p, 3d10–3d94f, 3d10–3d95p, and 3d10–3d95f were identified. The agreement with ab initio relativistic calculations is good. The relevance of the jj coupling scheme for level labeling is discussed, as is the importance of relativistic effects, by comparing the scheme with other results on high-Z atoms (up to Pt).

Soft X-ray bands of highly ionized tungsten, gold and lead emitted by the TEXT tokamak plasma☆

Spectra of highly ionized tungsten, gold and lead emitted from the TEXT tokamak have been recorded in the 20–70 A range by means of a grazing incidence, time-resolving spectrograph. The narrow and bright emission bands centered around 40, 45 and 50 A in Pb, Au and W respectively, and bands of lesser intensities at lower wavelenghts, are emitted by a very large number of superimposed lines originating from transitions of the type 4d104fn−4d94fn+1, 4d104fn−4d94fn5p and 4fn−4fn−15l (l=d, g). The isoelectronic analysis shows that at the electron temperatures prevailing in the present experiment, Te≈800 eV, there are no contributions to the bands from ions having a 4p64dn ground state. This, together with the experimental measurement of the electron temperature profile, indicates that the heavy ion impurity distribution in the tokamak plasma is very close to ionization equilibrium.

X ray and EUV spectroscopic measurements of highly charged tungsten ions relevant to fusion plasmas

Using high-resolution x ray and extreme ultraviolet (EUV) spectrometry, the line emission of W28+ - W50+ ions was measured at the Berlin Electron Beam Ion Trap (EBIT). Our study encompasses a wide range of wavelengths (5-800 A) and includes the observation of electric and magnetic dipole lines. The results of our measurements are compared with predicted transition wavelengths from ab initioatomic structure calculations.

Interpretation of laser produced Au and W X-ray spectra in the 3 keV range

Abstract The pattern at 3.5 keV in Au spectra recently identified as caused by multiple inner vacacies in Au 26+ -Au 27+ by Kiyokawa et al. is reinterpreted as unresolved 3d-5f and 3d-6f transition arrays in Au 47+ -Au 52+ . Comparison with the same pattern in tungsten spectra from laser-produced plasma supports the identification.

The x-ray emission spectra of multicharged xenon ions in a gas puff laser-produced plasma

Emission spectra of multicharged xenon ions produced by a laser gas puff are observed with high spectral resolution in the 8.5-9.5 and 17- wavelength ranges. Three different theoretical methods are employed to obtain 3l- ( to 10) wavelengths and Einstein coefficients for Ni-like . For the 3d-4p transitions, very good agreement is found between the experimental wavelengths and the various theoretical wavelengths. These accurate energy level measurements can be useful for studying the Ni-like xenon x-ray laser scheme. On the other hand, several intense spectral lines could not be identified as 3l- lines of Ni-like xenon, despite the very good agreement between the wavelengths and Einstein coefficients calculated for these transitions using the three different methods.

Dielectronic recombination of Ni-, Cu-, and Ar-like tungsten and barium through the low inner-shell excited configurations including collision processes

Level-by-level relativistic calculations of dielectronic recombination (DR) cross sections and rate coefficients for Ni-, Cu-, and Ar- like tungsten in the ground state were performed. Similar calculations were carried out for Ni-like barium for comparison. The most important low-lying inner-shell excited configuration complexes are taken into account, namely (3p3d)154141′ for Ni-like W and Ba, (3p3d)154s4141′ for Cu-like W, and finally 3p53d91, 3s3p63d71, and 3p54141′ for Ar-like W. These complexes give the dominant contributions to the total DR rate coefficients for kTe < 0.5 keV, and are still expected to give major contributions at higher electron temperature. Configuration mixing is taken into account when significant. The energy levels of the tungsten inner-shell excited DR channels are found to have typical j-j coupling characteristics, whereas those of Ni-like barium do not. The role of non-resonant radiative stabilizations is found to be generally minor for the Ni- and Cu-like ions. In contrast, for Ar-like tungsten these stabilizations are found to be very important. The DR rate coefficients for Cu-like tungsten are found to be very close in magnitude to those of the Ni-like ion. Some partial contributions to the DR rate coefficients are found to rise dramatically at very low electron temperature, a fact that has been observed experimentally for lighter ions. It is found that high-1 3p53d91 configurations, that were previously neglected, may have a significant contribution to the DR of Ar-like tungsten. The effect of electron collisions with the inner-shell excited ions is shown to influence the DR rate coefficient only at very high electron densities, greater than 1020 cm−3 for Ni-like W and greater than 1022 cm−3 for Ar-like W. In the Ni-like case at an electron density of 1023 cm−3 these collisions enhance the DR rate by about 30% at 5 keV, and by as much as a factor of 2 at 200 eV.