New Approaches for Characterizing Absorptive Nonlinearities

Speaker: Dr. John Fourkas, UMCP

Host: Physical Chemistry Faculty

Abstract: Multiphoton absorption is an important phenomenon in spectroscopy, imaging, nanofabrication, and many other applications. However, making an accurate measurement of the number of photons involved in a multiphoton transition in all but the simplest of systems can be quite challenging, particularly when multiple orders of absorption or other photophysical effects are present. The traditional approach to this problem involves making a log-log plot of some observable as a function of the irradiance. This scheme is typically limited by dynamic range and other issues. We have developed a new suite of techniques called 2-beam action (2-BA) spectroscopies that allow for the determination of the order(s) of absorption at a single value of an observable. I will discuss some examples of how these methods are allowing us to elucidate the behavior of systems with complex photochemistry and photophysics. I will also introduce the next generation of these methods, laser light amplitude modulation action (LLAMA) spectroscopies, which simplify implementation substantially.

Physical Chemistry Seminar