Collisional population channels of the state and their impact on the fluorescence analysis of extensive air showers

Experimental evidence is found for the presence of collisional excitation mechanisms populating the vibrational levels v ′ = 0 , 1 of the N2 ( C 3 Π u ) state in addition to electron impact excitation. Relative excitation efficiencies of the levels v ′ = 0 , 1 and 2 are calculated for low energy ( ∼ 10 keV ) electron beam excitation. A summary of our measured values for the quenching rate constants for v ′ = 0 and 1 by ground state molecular nitrogen and water vapour is given. The impact of vibrational relaxation within the N2 ( C Π u 3 ) state on fluorescence emission is discussed.