Fig. 9. a Spectral interval spanning the O IV  -  multiplet at 554 Å. b Branching line intensity ratios vs. raster position over the East solar limb. The upper set of values corresponds to the I(3/2-3/2)/I(1/2-3/2) ratio and the lower set to the I(1/2-1/2)/I(3/2-1/2) ratio. The full line shows the corresponding A-value ratio.