Photodissociation of some simple nitriles in the extreme vacuum ultraviolet region Original Research Article

The photodissociation process to produce the electronically excited CN fragments from CH3CN, C2H5CN and n-C3H7CN has been studied by using synchrotron radiation. The cross-sections for the photoabsorption and the production of CN(B 2Σ+–X 2Σ+) and CN(A 2Πi–X 2Σ+) emission were determined over the excitation wavelength range 30–150 nm (67 000–333 000 cm−1). The photoabsorption peaks were interpreted in terms of excitations to valence excited states and the Rydberg states. The quantum yield for the production of the excited CN fragment takes a maximum just below the excitation energy corresponding to the first ionization potential of each nitrile. With the length of the alkyl chain, the quantum yield for the production of CN(B 2Σ+–X 2Σ+) emission decreases drastically. Based on these experimental results, the spectral assignments of the photoabsorption bands and the photodissociation mechanism of nitriles were discussed.