Visible spectra of W8+ in an electron-beam ion trap

Abstract

To provide spectroscopic data for lowly charged tungsten ions relevant to fusion research, this work focuses on the ${\mathrm{W}}^{8+}$ ion. Six visible spectra lines from ${\mathrm{W}}^{8+}$ in the range of 420--660 nm are observed with a compact electron-beam ion trap in Shanghai. Furthermore, transition energies are calculated for the 30 lowest levels of the $4{f}^{14}5{s}^{2}5{p}^{4}, 4{f}^{13}5{s}^{2}5{p}^{5}$, and $4{f}^{12}5{s}^{2}5{p}^{6}$ configurations of ${\mathrm{W}}^{8+}$ by using the flexible atomic code (fac) and grasp package. Reasonably good agreement is found between our two independent atomic-structure calculations. The resulting atomic parameters are adopted to simulate the spectra based on the collisional-radiative model implemented in the fac code. This assists us with identification of six strong magnetic-dipole transitions in the $4{f}^{13}5{s}^{2}5{p}^{5}$ and $4{f}^{12}5{s}^{2}5{p}^{6}$ configurations from our experiments.