Photodissociation of some simple nitriles in the extreme vacuum ultraviolet region

Abstract

The photodissociation process to produce the electronically excited CN fragments from CH 3CN, C 2H 5CN and n-C 3H 7CN has been studied by using synchrotron radiation. The cross-sections for the photoabsorption and the production of CN ( B 2 Σ +– X 2 Σ +) and CN ( A 2 Π i – X 2 Σ +) 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 2 Σ +– X 2 Σ +) emission decreases drastically. Based on these experimental results, the spectral assignments of the photoabsorption bands and the photodissociation mechanism of nitriles were discussed.