Regarding the impedance, we noted that RR was very accurate, as can be understood graphically (Figure Figure (b)) and with the average impedance error (𝜀̅ , = 2.27% and 𝜀̅ , ≤ 3.00%, see Table ). These findings did not vary with the number of collocation points 𝑁 (see the values of each error for 𝑁 = 𝑀, 10 𝑀, and 100 𝑀 in Tables and, and in Figure ), and we validated them with ten synthetic spectra (Tables and, and the boxplots in Figure ). In this section, we studied the effect of the penalties 𝑃 and 𝑃 added in ℒ (𝜽) to handle DRTs with negative peaks. More precisely, we investigated for 𝑁 = 10 𝑀 𝑃 and each component of 𝑃 in to assess how well these functions could suppress oscillations and minimize the errors 𝜀 , and 𝜀 , . Interestingly, 𝑃 alone was not sufficient to suppress the oscillations created during RR, and we found in this case that 𝜀 , and 𝜀̅ , were close to the case without penalties (Table ). Moreover, the minimum of 𝜀 , was achieved using the second term in 𝑃 , while the finest impedance recovery (i.e., lowest 𝜀̅ , ) was obtained by combining 𝑃 and only the first term in 𝑃 .