EMISSION-SPECTRA OF THE RADICAL CATIONS OF DIFLUORODIACETYLENE, PERFLUOROPENTADIYNE-1,3, AND PERFLUOROHEXADIYNE-2,4 IN THE GAS-PHASE - A-]X BAND SYSTEMS AND THE LIFETIMES OF THE A-STATES

Emission spectra of the radical cations of difluorodiacetylene, perfluoropentadiyne-1,3, and perfluorohexadiyne-2,4 have been observed in the gas phase following excitation with low energy electrons. The band systems, which are detected in the 450-630 nm wavelength region, are assigned to the Ã2Πu→X̃2Πg, Ã2E→X̃2E, and Ã2E u→X̃2Eg electronic transitions of these three cations, respectively, by reference to their photoelectron spectroscopic studies. The vibrational fine structure of the emission spectra is interpreted, and the frequencies of most of the totally symmetric modes in the ground state of these cations are inferred. The lifetimes of the lowest vibrational level of the à excited electronic states have been measured to be 28±3 ns, 30±3 ns, and 46±2 ns for the cations of difluorodiacetylene, perfluoropentadiyne-1,3, and perfluorohexadiyne-2,4, respectively. © 1979 American Institute of Physics.