Experimental and theoretical study of the ground-state M1 transition in Ag-like tungsten

We present an experimental and theoretical study of the F-2(5/2) -> F-2(7/2) M1 transition in Ag-like W (W27+). The experiments employed the Shanghai permanent magnet electron beam ion trap, which has been developed especially for assisting spectroscopic diagnostics of edge plasmas for magnetic fusion devices. The theoretical value was obtained using the GRASP2K set of computer codes and included a comprehensive correlation study. The experimental M1 wavelength was measured as 3377.43 +/- 0.26 angstrom (3378.43 angstrom vacuum wavelength), whereas the calculated wavelength is in good agreement at 3381.80 angstrom. This good agreement shows the importance of fully understanding the electron correlation effects to predict the energy of the fine structure even in this, for tungsten, relatively simple case. (Less)