Electron-impact excitation of the $D {}^{3}Σ_{u}^{+}$ and $c_{4}^{'} {}^{1}Σ_{u}^{+}$ Rydberg states of $N_{2}$

Absolute optical-emission excitation functions have been measured for the

D {}^{3}Σ_{u}^{+} \to B {}^{3}Π_{g}

fourth positive system bands (

0, v^{''}

) with

v^{''} = 0, 1, 2, 3, 4, 5, 6

and for the

c_{4}^{'} {}^{1}Σ_{u}^{+} \to a {}^{1}Π_{g}

Gaydon-Herman singlet system bands (

0, v^{''}

) with

v^{''} = 0, 1, 2, 3, 4, 5

produced by electron-impact excitation of the

N_{2} X {}^{1}Σ_{g}^{+} (v = 0)

ground state, for incident electron energies ranging from threshold to 440 eV. We find that the

D \to B

emission has a principal maximum at 14.1±0.3 eV, a smaller maximum (83% of principal maximum) at 23 eV, and an

E^{- 3}

energy dependence for incident electron energies

E > 65

eV. Measurements over the energy range 13.5-31 eV indicate the

D \to B

emission is unpolarized. The sum over

v^{''}

of the

D \to B (0, v^{''})

optical-emission cross sections gives a maximum value 1.27 ×

10^{- 19}

{cm}^{2}

for the apparent cross section for the

v = 0

vibrational level of the

D {}^{3}Σ_{u}^{+}

state excited by electron collision with the

N_{2} X {}^{1}Σ_{g}^{+} (v = 0)

ground state. The appearance of two maxima in the

D \to B

optical emission is qualitatively confirmed by other experimental work. This point is discussed. For the

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Electron-impact excitation of theD Σu+3andc4′ Σu+1Rydberg states ofN2