SPECTROSCOPIC ANALYSIS OF THE NITROGEN SHORT-LIVED AFTERGLOW INDUCED AT 433 MHZ

A spectroscopic study involving N-2(B-3 Pi(g), V' = 11 --> A(3) Sigma(u)(+), v '' = 7), N-2(C-3 Pi(u), V'= 0 --> B-3 Pi(g), V '' = 0) and N-2(+)(B-2 Sigma(u)(+) = 0 --> X(2) Sigma(g)(+), v '' = 0) transitions is presented for description of the characteristics of the so-called short-lived afterglow (SLA) created by a nitrogen microwave discharge (433 MHz) at pressures in the range 1.5-10 hPa. The spatial investigation along the flow system reveals strong intensity gradients but an approximate constancy, in SLA, of intensity ratios of the first transition to the second and third one. Criteria drawn notably from these observations are proposed in order to estimate the extension of the main regions encountered in the afterglow. The maximum intensity of emissions in SLA, their location and the gas temperature are studied versus the transmitted microwave power, the gas velocity and the pressure. On the basis of the presented results, a kinetic model is built to describe the birth of SLA and its bulk features. The main role played by the vibrationally excited ground state molecule is discussed. A basic consequence is the strong interdependence of the Vibrational energy and the temperature profile for occurrence of the maximum of intensity in SLA.