Developing a High Power Electron Paramagnetic Resonance Spectrometer to Analyze Electron Spin Dynamics

Electron Paramagnetic Resonance (EPR) Spectroscopy is widely used to study electron spin dynamics of various systems.  Commonly available commercial high field pulsed EPR spectrometers, which are available up to 95 GHz, use radiation sources with milliwatt power to study systems with slow electron spin dynamics by using pulses which are hundreds of nanoseconds long.  In pursuit of studying systems with very fast electron spin dynamics (i.e. proteins and other biological systems at room temperature), we seek to develop an EPR system using UCSB’s Free Electron Laser (FEL) which operates using 240 GHz radiation and produces kilowatt power to generate pulses which are less than five nanoseconds long.  We seek to utilize a two-pulsed EPR experiment to unveil the characteristics of the local environments surrounding the electron spins.  Our primary objective is to develop a process to slice the existing microsecond-long pulse provided by the FEL into two separate pulses, each less than five nanoseconds long.  We have developed a pulse slicing procedure utilizing silicon switches that are activated by high-powered Yttrium Aluminum Garnet (YAG) lasers (532 nm wavelength).  We are considering improving the accuracy of the YAG lasers to optimize reflection of the silicon switches, implementing more efficient silicon switches, minimizing the background noise due to leaked radiation from various sources, and incorporating new YAG laser beam paths to allow greater variability of pulse length and duration between pulses.