Figure 4.

Component fitting to the ν_as(CN) band of urea during the transition from rehydrated to dry states. Four spectra were selected from the series obtained during drying of rehydrated urea of Figure 1. Times from beginning of the dehydration are indicated on each panel. Before fitting, spectra were corrected for effects of ramping caused by recording in ATR recording mode, followed by optimal fitting of the intensities of the four components of fixed frequencies and bandwidths (Table 4), together with unrestricted linear sloping baselines. (a) rehydrated; (b) and (c) intermediate partially-hydrated; (d) dry states. The residuals for each overall fit are shown underneath each panel at the same scale as the corresponding component fit, with the center line representing zero (that in Figure 3a consists largely of a residual water vapor component).