Detection of metastable excited molecules N ₂ (A ³ Σu ⁺ ) in an atmospheric pressure nitrogen discharge by Raman scattering

Raman scattering from metastable excited nitrogen molecules N 2 (A 3 Σu + ) created by an impulse discharge in nitrogen at atmospheric pressure was detected. A pulsed Nd:YAG laser at a wavelength of 266 nm was used as the light source, and Raman scattering from N 2 (A 3 Σu + ) at a wavelength of 277 nm was detected using an interference filter and photomultiplier tube. The filter had sufficient rejection of Rayleigh scattering of laser light at a wavelength of 266 nm and of Raman scattering from ground‐state nitrogen molecules N 2 (X 1 Σg + ) at a wavelength of 284 nm. The temporal variation of the signal intensity of Raman scattering from N 2 (A 3 Σu + ) was measured by transmitting the laser light at different time delays relative to sparkover. The results showed that the signal intensity decayed with a time constant of about 200µs.