Spectroscopic diagnosis of plasma in atmospheric pressure negative pulsed gas-liquid discharge with nozzle-cylinder electrode

The plasma characteristics of a gas-liquid phase discharge reactor were investigated by optical and electrical methods. The nozzle-cylinder electrode in the discharge reactor was supplied with a negative nanosecond pulsed generator. The optical emission spectrum diagnosis revealed that OH (A²∑⁺→X²Π, 306–309 nm), N₂ (C³Π→B³Π_g, 337 nm), O (3p⁵p→3s⁵s⁰, 777.2 nm) and O (3p³p→3s³s⁰, 844.6 nm) were produced in the discharge plasma channels. The electron temperature (T_e) was calculated from the emission relative intensity ratio between the atomic O 777.2 nm and 844.6 nm, and it increased with the applied voltage and the pulsed frequency and fell within the range of 0.5–0.8 eV. The gas temperature (T_g) that was measured by Lifbase was in a range from 400 K to 600 K.