Theoretical population ratios for different Fe II* transitions for T_e = 5000 K (determined from our CLOUDY modeling; dashed curves). The solid crosses represent the observed column density ratios and their corresponding error (which includes the error determined in Sect. 3.3). The arrows represent the lower limits obtained from possibly saturated troughs corresponding to these energy levels. The mean n_e along with its errors obtained from all the levels is shown in brown.