The electron beam excitation spectrum of N2at low pressure (0.12ndash;0.18mgr;) in the wavelength range 1200ndash;2000 Aring; was recorded for monoenergetic electron impact energies from 10 to 208 eV. The spectral features observed were the Lymanndash;Birgendash;Hopfield vibrational transitionslpar;a1Pgr;gthinsp;rarr;thinsp;1Sgr;gand several atomic nitrogen multiplets produced by dissociative excitation of N2. The emission cross sections of the Lymanndash;Birgendash;Hopfield vibrational transitions were measured and summed to give the cross section for the entire electronic transition. The energy dependence of all vibronic transitions was the same. The atomic nitrogen transitions studied were the multiplets at 1200 Aring;lpar;4Pthinsp;rarr;thinsp;4S0rpar;, 1493 Aring;lpar;2Pthinsp;rarr;thinsp;2D0rpar;and 1743 Aring;lpar;2Pthinsp;rarr;thinsp;2P0rpar;. These emissions originated from dissociative excitation of molecular nitrogen. The emission cross sections of these transitions typically have two thresholds, corresponding to dissociative excitation of N2into two nitrogen atoms and to dissociative ionization excitation into an atom and an ion.
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