Linear Dichroism in the NEXAFS Spectra of n-Alkane Crystalline Polymorphs

Abstract

Linear Dichroism in Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is a useful tool for studying molecular orientation and for clarifying spectroscopic assignments. n- Alkane molecules can form single crystals with different polymorphs; orthorhombic and monoclinic in the case of even chain lengths between n-C28H58 and n-C40H82. These polymorphs exhibit different linear dichroism in their NEXAFS spectra; in particular a backbone-oriented transition contributes to the low-energy “C-H” band in the monoclinic polymorph.