Figure 4.

SRS microspectroscopy and polarization dependence of CD₃CN adsorbed in SP-MOR. (A) SRS response of the C≡N stretch region of liquid CD₃CN (×0.2) and of CD₃CN adsorbed in SP-MOR (averaged over a whole crystal) recorded with lasers polarized in crystallographic b- (I_bb^SRS) and c-axes (I_cc); spectra are fitted by a single Lorentzian curve (solid line). (B,C) Polar plot for C≡N stretch (2275 cm^–1) in SP-MOR crystals with different crystal orientations shown in the insets as a function of θ (angle between laser polarization and crystallographic b-axis); the polar plots can be simulated by the sum (solid line) of a cos² θ function (anisotropic component, dashed line) and a circle (isotropic component, dotted line); scale bar: 5 μm. (D) Spectra for the anisotropic (I_bb^SRS – I_cc) and the isotropic (I_cc^SRS) components in the C≡N vibration.