Supercontinuum diagnostic for detecting solvated electrons produced by atmospheric pressure plasma

Contamination of groundwater by poly-fluoroalkyl substances (PFAS) is increasingly recognized as a major environmental issue. These compounds bioaccumulate, can cause adverse health outcomes, and are difficult to break down. Low temperature plasma (LTP) offers promising avenues to remediation, especially via the production of free electrons dissolved in water (“solvated electrons”). We present the design of recently-funded experiments focused on understanding this process. We plan to measure the time-dependent concentration of solvated electrons produced by atmospheric pressure plasma at the water’s surface using a pulsed supercontinuum light source. Supercontinuum transient absorption spectroscopy is a well-established method for studying time-resolved chemical and physical processes, but it has not yet been applied to LTP or to the plasma/water interface. By coupling supercontinuum transient absorption spectroscopy with the total internal reflection geometry of Rumbach, et. al (2015), we hope to obtain surface-sensitive measurements with nanosecond time resolution over a wide absorption band. We will describe the current diagnostic design and discuss the expected challenges, workarounds, and enhancement techniques that may be necessary to improve the signal to noise ratio.