Figure 1

A typical set of measured spectra for water/silica interfaces taken with $S_{\gamma }SP$ polarization combination and bulk $p\mathrm{H}=6.5$. The three spectra were taken with the output polarization set at $\gamma =0$ ($\square$), and $\gamma =\pm 5°$ ($▵$ and $▿$). The dotted horizontal line denotes the signal from bulk contribution alone, $S_Q(\gamma =\pm 5°)$. The inset depicts the sample stage and beam geometry.Reuse & Permissions

Figure 2

The magnitude ($\blacksquare$) and the real ($•$) and imaginary ($\circ$) parts of the nonlinear susceptibility of interfacial water, ${\chi }_S^{(2)}$, versus the input infrared frequency deduced from the measured sum-frequency spectra for three representative $p\mathrm{H}$ values of the aqueous solution. The solid curves are a guide to the eye.Reuse & Permissions

Figure 3

(a) Decomposition of spectra of $\mathrm{I}\mathrm{m}[{\chi }_S^{(2)}]$ (open squares and solid line) for different $p\mathrm{H}$ into a liquidlike component (dashed line) and icelike component (dotted line). (b) The icelike component (open circles and solid line) further decomposed into two subcomponents (dashed and dotted lines). For $p\mathrm{H}=3.0$ and 4.5, the dashed line coincides with the solid line as the high-frequency subcomponent (dotted line) of the icelike peak has approximately zero strength. (c) Strengths versus $p\mathrm{H}$ of the liquidlike component ($\blacksquare$), the $3000{\mathrm{c}\mathrm{m}}^{-1}$ ($▴$), and the $3200{\mathrm{c}\mathrm{m}}^{-1}$ subcomponent ($▾$) of the icelike component, as well as the overall integrated strength of the icelike component ($•$). The curves are a guide to the eye.Reuse & Permissions