Spectroscopic studies of open-shell organic cations in the gaseous phase: chlorodiacetylene and dichlorodiacetylene cations

Abstract

The application of the techniques of emission, laser-induced excitation and photoelectron-photon-coincidence spectroscopies to open-shell organic cations which decay radiatively are illustrated by such studies on chlorodiacetylene (òΠ_Ω↔X²Π_Ω) and dichlorodiacetylene (òΠ_Ω,u↔X²Π_{Ω, g}) cations. The emission and the laser-induced excitation spectra yield the vibrational frequencies of most of the totally symmetric fundamentals for these cations in their à and X states. Higher-resolution emission spectra reveal further structure. The detection of coincidences between energy-selected photoelectrons and emitted photons show that the radiative process depletes levels at least up to 3000 cm^–1 within their à states and the data give their fluorescence quantum yields and cascade-free lifetimes. It is shown how these methods provide complementary information on the spectroscopic structure and decay behaviour of open-shell cations.