The Ultraviolet Absorption Spectrum of Ammonia. III. The Absorption Spectra of the Deuteroammonias. A Note on Rydberg Series in Ammonia

Abstract

The absorption spectrum of mixtures of N${\mathrm{D}}_3$, N${\mathrm{D}}_2$H, and ND${\mathrm{H}}_2$ has been obtained from 2200 to 800A in a normal incidence vacuum spectrograph with a dispersion of about 8.5A/mm. The spectrum above 1675A (the end of the first electronic transition) is made up of very diffuse bands. Below 1675 all the bands are sharp. Two electronic transitions are found between 1675 and 1220A. Each electronic transition is accompanied by many vibrational transitions. Relatively long $v^{\prime }$ progressions are found for each of the molecules. Evidence for a fourth electronic state below 1220A was found, but no analysis of the bands could be made. Only one excited state frequency appears for each molecule. This is most probably the parallel deformation frequency, which is also the only frequency found for ammonia in the ultraviolet. The numerical values of the frequencies were calculated from ammonia frequencies in corresponding excited states considering changes in mass alone, and agreed with experiment. The electronic terms for the excited states were also calculated. A discussion is given of a possible Rydberg series in ammonia.