N I 8680- and 8629-angstrom multiplets in the dayglow

The N I 8680- and 8629-Angstrom multiplets have been observed in the midlatitude dayglow during moderate-to-high solar activity. A rocket-borne near-infrared spectrometer of 13.4-Angstrom resolution recorded spectra between 120 and 219 km. Analysis yielded altitude profiles of emissions including the N-2 first positive (1 PG) (2,1) band, the O-2 atmospheric (0,1) and (1,2) bands, and the N I 8680- and 8629-Angstrom multiplets. Photoelectron impact models adequately described the measured 1 PG profile but significantly underestimated the N I multiplet emission rates. It is suggested that the primary source of the multiplets is photodissociation of N-2. The contribution of this process was estimated from a model based on the shape of the N I 1200-Angstrom line's photoexcitation cross section. If the proposed excitation mechanism is correct, peak cross-section values for the 8680- and 8629-Angstrom multiplets would have to be 7.2 +/- 5.2 x 10(-20) and 5.7 +/- 3.2 X 10-(20) cm(2), respectively.