Value of ψ from Eq. (22) as a function of density for each typical EM from CHIANTI for the linear combinations of lines used in the LCR method. This time we use the coefficients listed in Table 1 computed at a fixed density of log n  =  8.3 and the contribution functions are evaluated at the different density values. The dashed lines correspond to the density value assumed for the optimisation, and to the target value of ψ.