The absorption spectrum of acetaldehyde in the vacuum ultra-violet

The absorption spectrum of acetaldehyde has been photographed in the vacuum ultra ­ violet. Three Rydberg series were found, all leading to the same limit. For the first of these no less than sixteen members were observed, enabling the ionization potential to be given as 10·1811 ±0·0007 V. This is the most extensive Rydberg series so far found in polyatomic molecules. The excited electron is one of the non-bonding 2py oxygen electrons. The nature of the electronic transitions responsible for the various regions of the spectrum is discussed.