Vibronic spectroscopy of jet-cooled p-cyanobenzyl radical: D1→D0 spectra and vibrational mode assignments

The jet-cooled p-cyanobenzyl radical has been generated from p-tolunitrile and vibronically excited with a carrier gas, He, using a pinhole-type nozzle in a corona excited supersonic expansion. The vibronic emission spectrum of the p-cyanobenzyl radical in the transition of D1(2 2B2)→D0(1 2B2) has been recorded with a long-path monochromator in the visible region. The spectrum was analyzed to obtain the vibrational mode frequencies of the p-cyanobenzyl radical in the ground electronic state with the aid of an ab initio calculation as well as those of p-tolunitrile.