Investigation of the orientation dependence on chiroptical properties of single molecules

• Main Author: Cyphersmith, Austin J
• Language: ENG
• Published: ScholarWorks@UMass Amherst 2013
• Subjects: Chemistry|Physical chemistry
• Online Access: https://scholarworks.umass.edu/dissertations/AAI3556240

Optical activity is the defining property of chiral materials that is essential for characterization in biology, chemistry, and physics. While a substantial body of research has provided a strong theoretical framework of the origin of optical activity, we still know very little by way of experiment about an individual molecule's contribution to the bulk optical activity. The chiroptical response of a single molecule can depend on molecular orientation and local molecular environment, information which is lost in ensemble averaging. This thesis focuses on establishing methods for a priori determination of chiral molecule orientations and refining measurements to probe the chiroptical response of a single molecule using a generalization of well-known defocused emission pattern imaging. Recent experiments probing the chiroptical response of single helicene dimer molecules offer new insight into the relationship between local molecular environment and coupling between chiral moieties. New experiments, such as probing the chiroptical response of an achiral, non-centrosymmetric molecular systems and polarization resolved spectral measurements which probe the Davydov splitting of coupled chromophore systems offer promising new avenues for understanding the connection between the polarization properties of single molecules and the ensemble.