A simplified mechanism is presented for excitation of ground state CN(X2Σ+) formed from carbonaceous impurity in flowing N2subjected to a microwave discharge. Analysis of absolute intensity data from spectrometer recordings of CN(B2Σ+ → X2Σ+) violet band emission enabled order of magnitude estimates of rate constants for CN(X2Σ+) excitation by energy transfer from vibrationally excited ground state nitrogen,and formation of electronically excited NCN* in a three body reactionEnergy transfer fromis shown to be a minor source of excitation of CN to radiative levels. N2(A) is a source of vibrationally excited ground state nitrogen,which in turn excites CN. Vibrational population profiles under all conditions in this work are shown to be primarily a function ofEvidence for the participation of theA2Π state of CN is shown in the population maxima at ν = 4 and 10 of theB2Σ+state.