Emission Cross Sections for theN2Second Positive (0, 0) Transition for H,H+, He, andHe+Impact

Absolute emission cross sections for 3371-Å radiation resulting from

C {}^{3}Π_{u} (v^{'} = 0) \to B {}^{3}Π_{g} (v^{''} = 0)

transition in molecular nitrogen have been measured for H,

H^{+}

, He, and

{He}^{+}

projectiles. The energy range covered was from 10 to 100 keV for all projectiles except

H^{+}

, where the lower limit was 40 keV. Excitation of the

C {}^{3}Π_{u}

upper state requires a spin change, usually accomplished by interchange of electrons. Thus the cross section for

H^{+}

impact is very small (≲

10^{- 19}

{cm}^{2}

) and could not be measured reliably below 40 keV at this time. Some emission cross sections are presented for incident helium atoms in the

2 {}^{3}S

metastable state. Comparisons are made of

{He}^{+}

and H data, where the minimum excitation energy required is the same, and of

{He}^{+}

and He data, where the minimum excitation energies are quite different. Cross sections are also presented for emission of the

N_{2}^{+}

(3914-Å) band for protons in the 8-30 keV energy range, permitting comparison with the measurements of other investigators.

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