Experimental and theoretical cross sections are reported for single-photon single ionization of W$^{ 5+}$ ions. Absolute measurements were conducted employing the photon-ion merged-beams technique. Detailed photon-energy scans were performed at (67$\pm$10)~meV resolution in the 20 -- 160 eV range. In contrast to photoionization of tungsten ions in lower charge states, the cross section is dominated by narrow, densely-spaced resonances. Theoretical results were obtained from a Dirac-Coulomb R-matrix approach employing a basis set of 457 levels providing cross sections for photoionization of W$^{ 5+}$ ions in the $4f^{ 14}5s^2 5p^6 5d \; { ^2}{ \rm D}_{ 3/2}$ ground level as well as the $4f^{ 14}5s^2 5p^6 5d \; { ^2}{ \rm D}_{ 5/2}$ and $4f^{ 14}5s^2 5p^6 6s \; { ^2}{ \rm S}_{ 1/2}$ metastable excited levels. Considering the complexity of the electronic structure of tungsten ions in low charge states, the agreement between theory and experiment is satisfactory.
Categories: physics.atom-ph