Reaction frequency of solvated electrons in water interacting with atmospheric-pressure helium plasma jet

Abstract

We employed the charge transfer to solvent (CTTS) transition of iodine negative ions to investigate the reactivity of solvated electrons in water interacting with an atmospheric-pressure helium plasma jet. A dye laser pulse at 225 nm was injected into the solution of potassium iodide, which was irradiated with an atmospheric-pressure helium plasma jet, and the reaction frequency of solvated electrons produced by the CTTS transition was measured by optical absorption spectroscopy. We observed the temporal and spatial variations of the reaction frequency of solvated electrons. We found that the reaction frequency of solvated electrons was determined by the concentrations of dissolved oxygen and hydrogen peroxide. We detected a high reaction frequency of solvated electrons in the limited depth region from the solution surface, indicating that hydrogen peroxide is localized near the plasma-liquid interface.

Detection of solvated electrons below the interface between atmospheric-pressure plasma and water by laser-induced desolvation

“…More recently, Sakakibara and coworkers detected hydrated electrons produced by laser-induced plasma in water [20], but it was not an experiment at the plasma-water interface. In previous works [21,22], we investigated the reactivity of solvated electrons in liquids interacting with plasmas by measuring the lifetime of solvated electrons produced by the charge transfer to solvent (CTTS) transition of iodide negative ions (I − ) [23]. However, these experiments were carried out in bulk liquids, and the solvated electrons we observed were not generated by the plasma-liquid interaction.…”

“…The rate coefficient k is known as k = 1.1 × 10 10 M −1 s −1 [17]. We assume ν = 8 × 10 6 s −1 in figure 6 according to our previous work [22], and equation ( 2) is normalized to the experimental data at [H 2 O 2 ] = 0 mM. A possibility in the laser-induced production process of free electrons in the solution is photodetachment of negative ions.…”

“…We assume ν = 8 × 10 6 s −1 in Fig. 6 according to our previous work [22], and Eq. ( 2) is normalized to the experimental data at [H 2 O 2 ] = 0 mM.…”