Photoionization Experiments with an Atomic Beam of Tungsten in the Region of the 5pand 4fexcitation

Abstract

An atomic beam of tungsten and photoexcitation with monochromatized synchrotron radiation were used to measure the first photoion yield spectra of W+ and W + in the region of 30 -60 eV. The comparison with calculated photoionization cross sections shows that the resonance structure can be explained by discrete Sp~Sd, 6s and 4f~Sd transitions if one takes into account the thermal population of the initial states 5d 6s Dp & 234 and 5d 6s 53.

Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

“…The data for single ionization of W + ions by Stenke et al [45] are in quite good agreement with preceding measurements by Montague and Harrison [47]. Photoionization of neutral tungsten atoms was previously studied in the energy range from about 27 to 60 eV by Sladeczek et al [48]. Before this measurement, photoabsorption experiments with neutral tungsten in solid and vaporized forms had been performed by Haensel et al [49] and by Costello et al [50], respectively.…”

“…A few years after that pioneering experiment the production of W + and W 2+ photo-ions from tungsten vapor was observed by Sladeczek et al [48]. However, no experimental data have been available in the literature for tungsten ions prior to the present project.…”

“…This work is close to being finalized. Figure 8 shows cross sections for photoionization of neutral tungsten atoms published by Sladeczek et al [48]. The top panel presents theoretical data obtained by the RHF approach.…”

“…Unfortunately, the population of excited levels in the DLP experiment is not known leaving ambiguity in any comparison with theory. [48] brought into the gas phase by evaporating tungsten at 3200 K. The resulting population of long-lived excited levels has been considered. No normalization procedures or energy shifts were applied to the two data sets.…”

“…Theoretical work using the many-body perturbation theory (MBPT) approach has been carried out by Boyle et al [64] for photoionization of neutral tungsten atoms in their 4f 14 5s 2 5p 6 5d 4 6s 2 5 D 0 ground level. Theoretical treatment of photoabsorption using a relativistic Hartree-Fock (RHF) approach was reported by Sladeczek et al [48] for all five levels of the 5d 4 6s 2 5 D ground term and for the 5d 5 6s 7 S 3 excited level. Because of the lack of experimental data for ionized tungsten atoms, an attempt was made in the present tungsten project to study photoionization of W q+ ions in charge states q ≤ 5.…”