Measuring Concentration of Solvated Electrons in Liquid Ammonia Generated using Atmospheric-Pressure Plasma

The interactions of solvated electrons at the plasma/liquid interface is not yet well-understood, but is an important area of many atmospheric-pressure plasma applications. Solvated electrons have a broad absorption band that provides an avenue to measure their concentration, but the signal read from one plasma pulse is typically negligible. Solvated electrons in water last only a few microseconds, however in anhydrous liquid ammonia this lifetime extends up to days. Due to this long lifetime, a cumulative signal can be detected as electrons are injected over time, even if the amount of electrons injected by each pulse of plasma is too small to measure individually. We use a source capable of generating repeating nanosecond-length high-voltage pulses to inject current into a liquid ammonia anode, and measure absorbance as a function of time using a 1550nm laser source. We present our experimental setup and preliminary measurements of solvated electron concentration.