Probing the negative ions and its role in self-organized pattern of a 1 atm DC Glow Discharge with Liquid Anode*

Plasma self-organization is a poorly understood process. Many hypotheses assume a reaction-diffusion system where electrons serve as the core activator and its diffusion, recombination, attachment are the inhibitor [1]. It is then crucial to understand the electron distribution throughout the discharge plasma under self-organization conditions. Research has shown the importance of the presence of oxygen gas [2] in pattern formation; and we have verified that self-organized pattern cannot be formed in a low oxygen (<5%) environment. It is conjectured that the reduction of oxygen partial pressure decreases electron losses due to the absence of processes such as dissociative electron attachment.

In this work, the role of attachment processes in pattern formation is explored. Rather than simply alter the partial pressure of oxygen, here we use photodetachment to affect the local electron density. A tunable pulsed laser is used to perform photodetachment in the threshold of some negative ion species, specifically O^- and O₂^- to determine whether the dissociative electron attachment loss is the major inhibitor. This limited scope activity aims to provide insight into mechanisms that provide a clearer understanding into how patterns form on the surface.

References:

[1] Rumbach, P., Lindsay, A. E., & Go, D. B. (2019). Turing patterns on a plasma-liquid interface. Plasma Sources Science and Technology, 28(10), 105014.

[2] Shirai, N., Uchida, S., & Tochikubo, F. (2014). Influence of oxygen gas on characteristics of self-organized luminous pattern formation observed in an atmospheric dc glow discharge using a liquid electrode. Plasma Sources Science and Technology, 23(5), 054010.