Experimental and theoretical study of visible transitions in promethium-like tungsten

Visible transitions of promethium-like tungsten (W¹³⁺) were studied using the Shanghai high temperature superconducting electron beam ion trap. The M1 transition between the ground state (4f¹³5s^{2 2}F) fine structure levels was measured to be at 549.95 ± 0.06 nm. Seven other lines from W¹³⁺ were also found and five of them were classified as belonging to transitions within the first excited configuration (4f¹²5s²5p). These lines were assigned with the help of relativistic configuration interaction calculations and collisional-radiative model predictions of the relative line intensities. (paper)