Development of time-resolved measurements for solvated electrons at the plasma/liquid interface*

Free electrons dissolved in liquid (“solvated electrons”) are hypothesized to be a key part of plasma/liquid chemistry but are difficult to measure in water.  We are developing a broadband transient absorption diagnostic to measure the concentration of solvated electrons at the plasma/liquid interface.  We use light from a sub-nanosecond, pulsed supercontinuum (FYLA Iceblink) and the total internal reflection geometry of Rumbach, et. al (2015) to sample a broad absorption feature in the thin layer immediately underneath the liquid surface.  Low-jitter timing allows us to localize the measurement relative to the start of the discharge, and lock-in detection allows access to the small signal.  A student-designed, inexpensive multichannel detector records time-resolved intensity in the 600-1150nm wavelength band.  We will describe the current status of the diagnostic, results to date, complementary measurements, and planned improvements.