Laser optogalvanic spectroscopy of N2 from the A3Σu+ metastable state in a corona excited supersonic expansion

A hollow cathode combined with a corona excited supersonic expansion has proven to be an efficient method of producing a stable discharge in a N2/Ar gas mixture. A high-resolution and rotationally cold absorption spectrum of the well-known (2,0) and (8,7) bands of the B3Πg ← A3Σu+ first positive system of N2 was recorded. It illustrates the sensitivity of the laser optogalvanic detection technique coupled to such an apparatus. A significant reduction of the linewidth and an enhancement of the signal-to-noise ratio were obtained. A high variational excitation process has been observed and is discussed.