Physics Colloquium

Ultrafast Quantum Dynamics in Molecules on Femtosecond and Attosecond Time Scales

Niranjan Shivaram
Assistant Professor of Physics and Astronomy Purdue University, West Lafayette, IN

Abstract: Ultrafast science aims to probe dynamics in atoms, molecules and materials on time scales of femtoseconds to attoseconds. The invention of femtosecond lasers has led to experiments that have provided great insight into the behavior of matter on these ultrafast time scales. More recently, the process of high-order harmonic generation (HHG) has allowed us to push time scales down to attoseconds. On top of this, HHG provides a table-top source of coherent extreme-ultraviolet and soft x-ray light which is ideal for studying electronic processes in various systems. In parallel with recent developments in HHG sources, Free Electron Laser (FEL) facilities have emerged as a bright source of ultrashort coherent x-ray light and are now being pushed to the attosecond regime. In this talk, I will first provide a brief overview of HHG and FEL attosecond sources and discuss the various methods used in probing ultrafast dynamics in the context of molecular systems. I will then present some recent results with a new approach based on Optical Kerr Effect spectroscopy to probe ultrafast dynamics on excited electronic states in molecules. Finally, I will discuss ongoing work in my ultrafast laboratory at Purdue University.

Bio: Niranjan Shivaram is an Assistant Professor in the Department of Physics and Astronomy and an affiliate of the Purdue Quantum Science and Engineering Institute at Purdue University. Before moving to Purdue in 2019 he was an Associate Staff Scientist at the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory within Stanford University. He received his PhD in Physics from the University of Arizona and did his postdoctoral research in the Atomic, Molecular and Optical Sciences group at Lawrence Berkeley National Laboratory. Niranjan is an experimentalist and his research interests are in the area of Ultrafast Atomic, Molecular and Optical Science. He is currently building an Ultrafast Science laboratory at Purdue University with a focus on using an attosecond/femtosecond extreme-ultraviolet high harmonic generation source to study ultrafast molecular processes employing non-linear optical techniques as well as photoelectron spectroscopy.