Dielectronic recombination process in laser-produced tantalum plasmas

Abstract

The 3d-4f and 3d-5f emission patterns occurring between 4.5 and 6.5 A in the spectra of laserproduced plasmas of highly ionized tantalum are studied, and the pseudocontinuum which underlies the former is interpreted. For the transition subarrays suspected to be responsible for the pseudocontinuum, the average wavelengths and widths are computed ab initio in the formalism of spinorbit-split arrays; these subarrays are proven to cover a continuous band of wavelengths. For their intensities, the dielectronic recombination (DR) process populates efficiently the upper configurations, which, in most cases, lie above the ionization levels. The autoionization and radiative-transition probabilities, and the DR coefficients, are computed ab initio, in the form of averages for whole configurations or subconfigurations of Cu-like tantalum. The compact formulas for these averages are valid in intermediate coupling, avoiding any diagonalization. All the needed radial integrals are computed by means of a relativistic parametric potential central-field code.

Dielectronic recombination of Ni-like ions through the 3d94ln′l′ (n′=4,5) Cu-like configurations

“…These quantities for Ta + have been previously calculated by Bauche-Arnoult er al. [12], and are in good agreement with the present results. In Ref.…”

“…In a previous work [12] configuration averaging methods for computing DR rate coefficients were proposed for mod- where AE, =E, -EI, E, being the statistically weighted average energy of the configuration and EI the ionization energy. AE, and kT, are expressed in eV.…”

“…In Ref. [12] the quantity XXgdAd; was calculated instead of XXAd, and a value of 2.66X 10' s ' was obtained, compared to 2.86X 10' s ' for the same quantity using the present computation method. For XgdA&z the values calculated in Ref.…”

Broad M-band multi-keV x-ray emission from plasmas created by short laser pulses

“…9 Different studies on Au, Ta, Pb, Sm, Gd, and Dy emission ͑M-shell͒, realized in some laboratories, pointed out the specific 4f-3d intense emission. [10][11][12] Most of these studies were realized in the nanosecond regime. Spectra were observed to be composed of a myriad of transition arrays as well as individual lines.…”

Accounting for highly excited states in detailed opacity calculations

“…The contribution of dielectronic satellite transition arrays, with spectator electrons in shell n=5, was studied by Bauche-Arnoult et al for the case of a tantalum plasma [4]. The main mechanism for the formation of doubly-excited states is the dielectronic recombination.…”