Experimental determination of line-intensity ratios for the n=3 to n=2 transitions of O v, F vi, and Ne vii at electron densities in a range of (4–9)×${10}^{12}$ ${\mathrm{cm}}^{\mathrm{-}3}$

This paper reports relative-line-intensity measurements of the n=3 to n=2 transitions for O v, F v i, and Ne v i i in an electron density range of (4–9)×${10}^{12}$ ${\mathrm{cm}}^{\mathrm{-}3}$ in a tokamak plasma. Large discrepancies were found between the experimentally measured and theoretically computed values. The discrepancies are due to inaccuracies in the computations of the electron collision strengths from the 2$s^2$ and 2s2p levels to the 2s3p levels, using either the R-matrix method or the distorted-wave approximation.