Observation of N2(A³SIGMA+u) Metastable in Pulsed Positive Corona Discharge Using Laser-Induced Fluorescence

Relative density and spatial distribution of N
₂
(A
³
Sigma
_u

⁺
) metastables are measured in pulsed positive corona discharge using laser-induced fluorescence (LIF) under atmospheric pressure. The vibrationally ground state N
₂
(A
³
Sigma
_u

⁺
, v"=0) is excited to N
₂
(B
³
Pi
_g
, v"=4), then the fluorescence from (B
³
Pi
_g
, v"=4) to (A
³
Sigma
_u

⁺
,v"=1) is detected. The discharge occurs between a 12-mm point-to-plane gap in nitrogen or oxygen-nitrogen mixture. It is shown that the spatial distribution of N
₂
(A
³
Sigma
_u

⁺
) metastables is approximately uniform between the discharge gap. It indicates that N
₂
(A
³
Sigma
_u

⁺
) is mainly produced in the primary streamer channel, not in the secondary one. It is observed that, as well known, the decay rate of N
₂
(A
³
Sigma
_u

⁺
) density after discharge increases with O
₂
concentration. The rate constant of N
₂
(A
³
Sigma
_u

⁺
)+O
₂
is estimated to be 2.6times10
^-2
cm
³
/s.