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A non-tomographic analysis method is proposed to determine the 3D angles and the order parameter of molecular orientation using polarization-dependent infrared (IR) spectroscopy. Conventional polarization-based imaging approaches provide only 2D-projected orientational information of single chromophores or vibrational modes. The newly proposed method concurrently analyses polarization-dependent absorption profiles of two non-parallel transition dipole moments. The relative phase angle and the maximum-to-minimum ratios of the two polarization-dependent absorption profiles are used to calculate the 3D angles and the order parameter of molecular orientation. The relativity of those intermediate observables makes the analysis output values unaffected by variations in concentration, thickness, absorption peak, and absorption cross-section, which can occur in typical imaging conditions. This analysis is based on a single-step, non-iterative calculation that does not require any analytical model function of an orientational distribution function. This concurrent polarization analysis method is demonstrated using two simulation data examples and the error propagation analysis is discussed as well. Application of this robust spectral analysis method to polarization IR microscopy will provide a full molecular orientation image without tilting that tomographies require. In this talk, I describe this new approach that non-iteratively determines the 3D angles and the orientational order parameter without assuming a model function for an ODF. Then, I will demonstrate an application of this analysis using experimental image data acquired from a semicrystalline polymer film with polarization IR microscopy. The results clearly show how the 3D angles and the order parameter are determined for every pixel using straightforward formulas without iterative calculation.
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