Fig. 3. Results of the Lorentzian fitting of the VSFG spectra. The sum of all fitted peaks is shown on the top left. The different panels present the 1066 cm⁻¹ (top middle), 1075 cm⁻¹ (top right), 1084 cm⁻¹ (bottom left), 1093 cm⁻¹ (bottom middle), and 1100 cm⁻¹ (bottom right) peaks fitted to the spectrum of DPPC on a 2.8 mM Ca²⁺ subphase without (black traces) and with (red trace) CS. As a control, the panels also contain the corresponding fitted spectrum and peaks of DPPC on pure H₂O (green traces). The fitting parameters are listed in Table S1 in the ESI.†.