Regular Article

Analysis of EUV spectra from N-shell tungsten ions observed with an electron beam ion trap

National Institute of Standards and Technology, Gaithersburg, MD 20899-8422, USA

^d e-mail: yuri.ralchenko@nist.gov

Received: 14 March 2018
Received in final form: 11 May 2018
Published online: 3 July 2018

Abstract

Extreme ultraviolet spectra of highly charged tungsten ions were produced with an electron beam ion trap at the National Institute of Standards and Technology and recorded with a flat-field grazing-incidence spectrometer. The spectra were measured in the wavelength range 2.7–17.3 nm while the beam energy varied between 1.65 and 2.00 keV. At these energies, the ionization stages from Zr-like W³⁴⁺ to Se-like W⁴⁰⁺ ions were observed. Large-scale collisional-radiative modelling was used to identify the strong lines, including 15 new ones, which represent electric dipole n = 4–4 transitions in these ions. While a good quantitative agreement between theoretical and experimental data was found for almost all ions, some of the tentatively identified wavelengths in W³⁵⁺ significantly disagree from all available calculations.