Electron-impact excitation of the vibrational levels of the c4/sup '/ 1Σ/sub u/+ electronic state of the nitrogen molecule

Electron-impact excitation of the excited vibrational levels of the c4/sup '/ 1Σ/sub u/+ state of the nitrogen molecule has been studied. We measure the electron-impact optical emission cross sections of the (1,2), (4,0), and (4,1) vibration bands of the c4/sup '/→a electronic transition of the nitrogen molecule and compare them with the direct electron-impact cross sections of the c4/sup '/(v') vibrational levels reported in the literature. The Franck-Condon factors between the ground vibrational level of the X 1Σ/sub g/+ ground electronic state and the various vibrational levels of c4/sup '/ have been calculated and compared with the electron-impact cross sections. The excitation cross sections of the v' = 4 level of c4/sup '/ are several orders of magnitude higher than predicted by the Franck-Condon picture. This discrepancy is due to the perturbations of the c4/sup '/(v' = 4) level by the b' 1Σ/sub u/+ state