Chemistry Weekly Seminar - Sahan Neelakanni
Sahan Neelakanni, PhD candidate, will present a seminar.
Systematic Investigation of Intermolecular Interactions in Near Edge X-ray Absorption Spectroscopy (NEXAFS)
Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy can be used to study molecular packing and order in organic materials, if the effect of intermolecular interactions on this spectroscopy is understood. This work aims to contribute towards a general understanding of intermolecular effects on NEXAFS spectroscopy by studying the variation in Rydberg-valence interactions for saturated molecules and π-π interactions for unsaturated molecules.
The effect of π-π interactions with the spacing between co-facial benzene rings is significant and could provide a mechanism to study molecular packing and order in unsaturated materials. Orthorhombic and monoclinic n-alkane single crystals were used to study Rydberg-valence mixing in saturated molecules. In the NEXAFS spectra of crystalline n-alkanes, different crystalline environments are found to not have a significant effect on the NEXAFS spectra. However, a contribution from nuclear motion to broadening of the NEXAFS features was observed; this broadening varies with the n-alkane chain length. Nuclear motion refers to the energetically accessible molecular conformations present at the experimental temperature. Intermolecular interactions and different nuclear motions of a molecule modify the NEXAFS spectroscopy.