Absolute intensity of luminol chemiluminescence induced in vicinty of water surface irradiated with atmospheric pressure helium dc glow discharge

We propose a method for estimating the absolute densities of short-lived species just below the plasma-liquid interface. The method is based on the measurement of the absolute emission coefficient (the number of photons emitted per unit volume and unit time) of the luminol chemiluminescence induced by the plasma-liquid interaction. We constructed a simplified rate equation model which simulates the reaction processes of luminol, and the experimental emission coefficient was compared with the solution of the rate equations. If we have the agreement between the experiment and the simulation, the densities of short-lived species in the simulation give us their estimations. The experiment was carried out using an atmospheric-pressure helium dc glow discharge produced between a needle anode and a liquid cathode with luminol. The experimental emission coefficient was 2×10²⁵ m⁻³ s ⁻¹ assuming 10 µm for the thickness of the chemiluminescence region. The emission coefficient obtained by the simulation was 3 × 10²⁵ m⁻³ s ⁻¹ , which was in close agreement with the experimental result. However, the simulation model has many uncertain assumptions, and the modification of the simulation model is a future issue.