Each pair of peaks is given by two Lorentzians of opposite sign, as in equation 15. In the fit to the first hydration shell spectrum, was taken to be 100 cm -1 , based on the simulated symmetric and asymmetric stretch results (Figure ), and A, , and were free parameters for each pair. In the fit to the N-H-bound water spectrum, we used 100 cm -1 for the lower frequency pair and obtained 150 cm -1 for the higher frequency pair from the fitting. We identify the symmetric and asymmetric stretch components from the fit (red and blue lines, Figure ) using the knowledge that the asymmetric stretch has a higher frequency than the symmetric stretch because the typical intramolecular coupling is negative. Accordingly, we can add all symmetric contributions (dashed red lines, Figure ) from the fit to yield the total symmetric response (solid red line, Figure ). Similarly, we can also add all asymmetric contributions (dashed blue lines, Figure ) to obtain the total asymmetric response (solid blue line, Figure ).