THE VACUUM ULTRAVIOLET SPECTRUM OF AMMONIA

Author Institution: Division of Pure Physics, National Research Council“The absorption spectrum of ammonia, shows several band systems between 1675 and 1150 \AA. One band system, consisting of a single progression of bands originating at about 60,$130 cm^{-1}$, has been photographed a high resolution and complete rotational analysis of several bands has been achieved. The lines in the bands show the frequency and intensity patterns expected for a transition moment perpendicular to the figure axis thus showing that the upper state is a degenerate (E) electronic state. The analysis shows that the excited state is planar and that the progression of bands results from successive vibrational levels of the out-of-plane bending $(\nu_{2})$ vibration of the molecule in this state. The rotational levels of the excited state show a number of anomalies which are presumed to arise from an interaction between the vibrational and electronic motion.