We use a multitude of vibrational techniques including broadband femtosecond stimulated Raman (FSRS), impulsive stimulated Raman (ISRS) and resonance Raman spectroscopies (RRS) to answer questions such as which nuclear motions lead to efficient electronic coupling and chemical reactivity for the purpose of energy capture and transport in a variety of important semi-conductor systems. Additionally we are tackling fundamental optical questions such as ‘how does FSRS respond to field enhancement?’ and ‘how can we understand vibrational frequency resolution in the limit of Fourier uncertainty?’.
Reaction dynamics in Semi-Conductors
Broadband femtosecond stimulated Raman is an ultrafast spectroscopy technique which allows us to measure of molecular vibrations which govern light driven chemical and solid state reactions. By following how molecules and solids distort after they have been excited by light, we gain structural insights which inform the rational design of the next generation high efficiency photovoltaics.
Impulsive Stimulated Raman
Low frequency Raman active optical phonons carry an abundance of information about structure and reactivity of crystalline systems. To measure these frequencies we us an ultrafast impulsive pump-probe technique called impulsive stimulated Raman spectroscopy. Unlike standard Raman spectroscopy, ISRS allows us to measure vibrations on the excited state where the potential energy surface is modified and may be reactive. Understanding this reactivity will lead to improved materials design.
Resonance Raman Spectroscopy
Resonance Raman intensity analysis remains the industry standard for determining the geometry of an excited state potential energy surface. Unfortunately, the conventional wavepacket model is only applicable to isolated electronic transitions while the most robust photovoltaic systems often have congested electronic structure. We are working to extend this time tested analytic technique to more complicated solid state systems.