The Ultraviolet Absorption Spectrum of Ammonia

The discrete absorption spectrum of ammonia has been photographed from 2300 to 850A. The experimental results of other workers in the long wave portion of the spectrum are confirmed, and much new experimental data at shorter wavelengths found. The bands down to 1665A are all diffuse because of predissociation. Below 1665 all the bands are very sharp and show rotational fine structure which is partly resolved. True continuous absorption (in distinction to that produced by pressure broadening) does not begin until about 1200A. At 1150A and below the continuous absorption is so strong that no more bands could be measured accurately. Sharp bands exist, however, at least as far down as 1085A, so the first ionization potential should be at least 11.3 volts. The bands are classified in four $v^{\prime }$ progressions which fall in four different electronic states, all of the same type. All bands come from $v=0\mathrm{}$ of the normal state. Only one fundamental frequency appears in the excited states.