EUV photoabsorption of laser produced tellurium plasmas: Te I–Te IV

Abstract

The photoabsorption spectra of Te I through to Te IV have been recorded in the extreme ultraviolet (EUV) region using the dual laser plasma (DLP) technique. Photoexcitation from the 4d subshell is the dominant process in the 50 to 130 eV region. Above the 4d ionization thresholds the spectra were found to be dominated by a 4d →ϵf shape resonance which peaks at 88 eV in each case, indicating that complete 4f ‘collapse’ has not occurred in stages up to and including Te3+. A transfer of oscillator strength from the resonance to the pseudo-discrete 4d →nf (n ⩾ 4) transitions with increasing ionization is evident from Te2+ onwards with the transition being the strongest feature in the Te IV spectrum. Time-dependent local density approximation (TDLDA) calculations successfully account for the shape resonance while Hartree–Fock with configuration interaction calculations permit identification of the discrete features.

Extreme ultraviolet photoabsorption spectra of the Ce VI–Ce X isonuclear sequence

“…In each of the spectra analysed here a mixture of ionization stages contributed. For plasmas produced under our experimental conditions, previous results [6][7][8][9][10][11][12][13] have shown that the relative ion populations can be estimated by employing the collisional radiative model of Colombant and Tonon [17]. The relative populations at different electron temperatures are shown in figure 2.…”

“…Spectra were recorded electronically using the dual laser plasma (DLP) technique, which involves the generation of both the absorbing species of interest and a synchronized bright backlighting source using two laser-produced plasmas [8]. The DLP technique is a versatile, unique and effective diagnostic tool for photoabsorption spectroscopy and has been successfully used for the study of low, intermediate and high ion stages [6][7][8][9][10][11][12][13]. In this experiment, a Nd:YAG 850 mJ 15 ns (full width at half-maximum, FWHM) Q-switched laser pulse tightly focused onto a tungsten rod generated a tungsten backlighting continuum emitting plasma formed at a power density approaching 1 × 10 12 W cm −2 .…”