Fig. 4

Charged solid/water interface. SFG intensity spectra for two oscillators on a charged surface simulated for ω ₁ = 3200 cm⁻¹, γ₁ = 0°, ω ₂ = 3400 cm⁻¹, γ₂ = 180°, A ₁ M ₁ = A ₂ M ₂ = 10, Γ ₁ = Γ ₂ = 120 cm⁻¹, χ⁽³⁾ ₁ = 500, and χ⁽³⁾ ₂ = 150 using charge densities of + 0.001 (purple), −0.005 (blue), −0.025 (green), −0.05 (yellow), −0.17 (orange), and −0.25 (red) C/m² and a constant ionic strength of 0.1 M calculated without a and with b absorptive-dispersive interactions. c, d Same as in a, b but for ionic strengths that vary with charge density as in A and B as follows: 10 mM at + 0.001 C/m² (purple), 100 μM at −0.005 C/m² (blue), 40 μM at −0.025 C/m² (green), 40 μM at −0.05 C/m² (yellow), 100 μM at −0.17 C/m² (orange), and 10 mM −0.25 C/m² (red). e, f Im(χ⁽²⁾) spectra with ω ₁ = 3200 cm⁻¹, γ₁ = 180°, ω ₂ = 3400 cm⁻¹, γ₂ = 0°, A ₁ M ₁ = A ₂ M ₂ = 10, Γ ₁ = Γ ₂ = 120 cm⁻¹, χ⁽³⁾ ₁ = 500, and χ⁽³⁾ ₂ = 250 calculated using charge densities of + 0.2 (blue) and -0.2 (red) C/m² and a constant ionic strength of 100 μM, without e and with f absorptive-dispersive interactions