N I 8680‐ and 8629‐Å multiplets in the dayglow

The N I 8680‐ and 8629‐Å multiplets have been observed in the midlatitude dayglow during moderate‐to‐high solar activity. A rocket‐borne near‐infrared spectrometer of 13.4‐Å 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‐Å 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‐Å line's photoexcitation cross section. If the proposed excitation mechanism is correct, peak cross‐section values for the 8680‐ and 8629‐Å multiplets would have to be 7.2 ± 5.2 × 10 −20 and 5.7 ± 3.2 × 10 −20 cm 2 , respectively.