Departure coefficients b_i for P II (black), P III (red), P IV (blue), and P V (green) levels as a function of the Rosseland optical depth τ_R for the six selected sample stars. In the bottom right of each plot the name of the star together with its T_eff and log g-value are given. The colourmatching shaded areas indicate the formation depth of the strongest observed line for each ion. The curves are labelled with the identifiers listed in Table 3.