The N-2+O+ charge-exchange reaction and the dayglow N-2(+) emission

Dayglow spectra were recorded by the Arizona Airglow Experiment from the pa yload bay of the shuttle, STS-74. These spectra are used to reexamine the r ole of the prominent N-2(+) first negative emission from the dayglow thermo sphere. Many reports of the N-2(+) emissions identify problems in validatin g the intensity of the emission. Also, an extended vibrational and rotation al structure of the bands remains unexplained in the historical analysis. T hese anomalies appear to be due to the charge-exchange reaction, N-2+O+(D-2 ,P-2) --> N-2(+)+O, which is the dominant source of N-2(+) ions in the sunl it atmosphere at high altitudes. In the present work the N-2(+) emission wa s considered to originate from two separate ion sources. First are those em issions originating from ions produced by photoionizaton and electron bomba rdment; these emissions can be modeled. Second are the emissions originatin g from ions produced by the charge-exchange reaction; these emissions canno t be modeled. Synthetic emission profiles due to the first ion source were modeled and subtracted from the observed spectrum, leaving emission profile s resulting from the charge-exchange ion source. These residual vibrational and rotational profiles were analyzed to retrieve resonance scattering rat es for these ions. These scattering rates can be used to estimate the N-2() first negative emission rate expected from the thermosphere with a model of the atmosphere. It is suggested that measurements of the N-2(+) emission rate can be used to determine the daytime concentration of the oxygen ion, O+(D-2,P-2). Although the present work appears to resolve the question of the extended vibrational and rotational band structure, it does not help th e excess intensity problem significantly. It does point out that O+ must pl ay an important role in intensity problems.