Per-and polyfluoroalkyl substances (PFASs) are hazardous, carcinogenic, and bioaccumulative contaminants found in groundwater, surface water, and a wide variety of consumer products. The strong carbon-fluorine (C-F) bonds in these artificially-made compounds endow them with exceptional chemical stability and prevents most organisms from decomposing these persistent contaminants, which further exacerbates their bio-accumulation and toxicity. To mitigate and remove these persistent pollutants, many experimental efforts have focused on chemical oxidation approaches to accelerate their degradation. In particular, oxidative conditions have been applied to both perfluorooctanoic acid (PFOA; see Figure ) and perfluorooctane sulfonic acid (PFOS) contaminants. However, PFOS is more chemically resistant and more challenging to treat by conventional methods, such as chemical oxidation/reduction, and thermal decomposition. Among the various reducing agents, hydrated electrons have recently garnered significant attention for PFAS degradation because of their extremely negative reduction potential of -2.9 V. As such, experiments have shown that these short-lived, aqueous species react with a multitude of quenchers in microseconds via a one-electron transfer mechanism. Over the past several years, a variety of approaches have harnessed hydrated electrons to chemically dissociate perfluorinated compounds. For example, previous studies have used UV photolysis to generate hydrated electrons via energetic photons for defluorinating PFOS. However, UV photolysis inherently has a low quantum yield, resulting in a myriad of other side reactions and a slow defluorination rate. UV photoirradiation of sulfite, iodide, dithionite, and ferrocyanide has been used to decompose PFASs in aqueous media, and the success of these reduction techniques has been ascribed to hydrated electron generation based on scavenging experiments. Previous studies have also shown that some of the hydrated electrons produced from the photoirradiation of sulfite/iodide can be scavenged by oxidizing agents, which reduces the overall efficiency of the degradation process. Several researchers have addressed this problem by using nitrilotriacetic acid, indole derivatives, or organomodified montmorillonite to more efficiently generate hydrated electrons to destroy PFAS. Regardless of the specific experimental approach, the use of hydrated electrons has been shown to effectively reduce both PFOA and PFOS when used in sufficiently large quantities and in a conducive environment (i.e., correct pH, solute concentration, and temperature). Despite their effectiveness, a detailed mechanistic and atomistic understanding of how these hydrated electrons accelerate PFAS degradation remains unclear. Of the numerous experimental studies on PFAS degradation with hydrated electrons, most have either lacked the spectroscopic resolution to resolve these ultrafast dynamics or used fairly crude theoretical approximations. For example, several experimental studies have examined PFAS degradation products with hydrated electrons generated by ultraviolet light or electrodes; however, these approaches were not able to provide time-resolved details of the degradation mechanism itself due to the short timescales of these processes. However, there have been a few studies in the scientific literature that have explored time-resolved PFAS degradation kinetics with either hydroxyl radicals 33 or hydrated electrons. In particular, pulse radiolysis experiments by Szajdzinska-Pietek have shown that PFOA is largely unreactive with hydroxyl radicals, resulting in biomolecular rate constants far lower than ∼ 10 7 M -1 s -1 . Huang and co-workers explored photochemical reductive degradation (which produces hydrated electrons) of short-and long-chain PFASs and showed that the rate constant increases with chain length. Recently, the rate constants and activation energy associated with the initial reduction of PFASs were measured using temperature-dependent transient absorption spectroscopy, which showed no significant differences in the activation energy and rate constants associated with PFOA or PFOS degradation.