The Molecular Spectrum of Ammonia II. The Double Band at 10μ

Structure of the N${\mathrm{H}}_3$ absorption band at 10μ.—The N${\mathrm{H}}_3$ absorption band extending from 8μ to 14μ has been sufficiently resolved by means of a grating to reveal the details of its structure. Two very narrow zero branches of nearly equal intensity appear at 10.3μ and 10.7μ, with each of which there is associated a positive and a negative branch consisting of ten or twelve lines spaced at nearly equal frequency intervals. The mean spacing for the higher frequency series is 18.7 ${\mathrm{cm}}^{-1\mathrm{}}$, and for the lower frequency series 20.2 ${\mathrm{cm}}^{-1\mathrm{}}$. Both of these bands must be associated with a single fundamental vibration parallel to the symmetry axis.