Electronic spectrum of jet-cooled cyanocyclopentadienyl radical

The D₁-D₀ electronic spectrum of jet-cooled cyanocyclopentadienyl (C₅H₄CN) radical, produced by excimer laser photolysis of 1,3-cyclopentadiene-1-carbonitrile (C₅H₅CN), was measured by laser-induced fluorescence (LIF). The LIF spectrum was identical to that of radicals produced by photolysis of phenyl isocyanate and o-chloroaniline, which had been assigned to phenyl nitrene. This result shows that the nascent radical product in the photolysis of o-chloroaniline and phenyl isocyanate is isomerized to C₅H₅CN and the final product of C₅H₄CN radical is derived via the second photolysis. The rotational contour of the 0-0 band of the C₅₄CN radical, at 27143 cm^-1 (368.3 nm), is also presented. The electronic transition is A-type and π electron transition, and the symmetry of both the ground and excited electronic state is ²B₁ (of the C_2v point group).