AbstractWe have calculated the Fe XXIII spectrum in the collisional-radiative model including all fine structure transitions among the 2s2, 2s2p, 2p2, 2snl, and 2pnl levels where n = 3 and 4, adopting data for the collision strengths from H.I. Zhang and D.H. Sampson (At. Data Nucl. Data Tables 52 1992 143) and from D.H. Sampson, S.J. Goett and R.E.H. Clark (At. Data Nucl. Data Tables 30 1984 125). We present five ratios of spectral line intensities in the UV region and five ratios in the X-ray region as a function of electron temperature and density at 0.3 keV ≲ Te ≲ 10 keV and ne = 105–1023 cm−3 . Some ratios can be used for temperature diagnostics. The effect of cascades in these line ratios is discussed.