Observation of 1 D − 1 S forbidden optical emission of atomic oxygen in atmospheric‐pressure N 2 /O 2 plasma jet

We observed green optical emission from an atmospheric‐pressure N 2 /O 2 plasma jet. The green optical emission was composed of a line emission at λ  = 557.71 ± 0.03 nm and a broadband component at 530 ≤  λ  ≤ 560 nm . The line emission was assigned to the 1 D − 1 S forbidden transition of atomic oxygen, whereas the broadband emission was due to the formation of O( 1 S )N 2 excimer. We measured the absolute densities of O( 1 S ) and O( 1 S )N 2 using a spectrograph with the absolute sensitivity calibration, and we discussed the kinetics in the green plasma jet on the basis of the absolute O( 1 S ) and O( 1 S )N 2 densities. According to the rate coefficients and the transition probabilities reported in literature, the present experimental results are explained if the densities ofN 2 ( A 3 ∑ u + )and O( 3 P ) are 9 × 10 13 and 3 × 10 13 cm −3 , respectively.