  The atomic states of the W IX (W8+) tungsten ion lying below the W9+
ionisation threshold have been studied theoretically, employing the
multiconfiguration Dirac-Hartree-Fock method with configuration interaction.
The level electronic structures and their energies are presented. The electric
dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic
quadrupole (M2) radiative transitions have been computed in order to calculate
the radiative lifetimes of given states. Transition wavelengths, energies, and
decay rates are also presented for selected high-intensity E1 transitions. The
configuration interaction method was applied to estimate electron correlation
effects. The aim of the present research was to fill a lack of atomic data for
low-charged tungsten ions, which may be useful in low-temperature plasma
diagnostics and may form the base for collisional-radiative modelling of
spectra for low-charged tungsten ions.
