The Grating Infrared Solar Spectrum. III. Rotational Structure of the Carbon Dioxide (CO₂) Band ν₂ at 13.9 μ.

The rotational structure in the positive branch of the carbon dioxide band [(v1, 2v2) - p2], centered at 13.9 j~, is extensively developed in the solar spectrum between 13.9 ~ and 13.0 ~. Rotational levels through quantum number J = 64 are represented. The rotation lines are satisfactorily ordered by the expression vcm-~ = 720.71 + 0.789 N - 0.00051 N2, where N is the ordinal number of the line. The equilibrium moment of inertia of the CO2 molecule deduced from the observations is A = 70.8 X i~4° gm cm2, in excellent agreement with laboratory determinations and with the value obtained from the CO2 bands in the spectrum of Venus. The low transmission of the terrestrial atmosphere between the ailternative long wave-length limits of transmission ~ j~ and ~ ~ is evident in the grating solar spectrum of this region