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 (4f135s2 2F) 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.