From fluorescence quantum yields fgr;Fand lifetimes tgr; measured by the threshold photoelectronndash;fluorescence photon coincidence (Thyphen;PEFCO) method, reported in a companion paper, the radiativekrand nonradiativeknrrelaxation rates have been determined for energy selected states of 1,3,5,hyphen;C6F3H+3and C6F+6.knris less than 106sminus;1in theBtilde; state energy region of 1,3,5,hyphen;C6F3H3+; an exponential dependence ofknras a function of the selected energy was found in theCtilde; andDtilde; energy regions of this ion. The nonradiative relaxation of fluorescent states of 1,3,5,hyphen;C6F3H+3and C6F+6involves coupling to high vibrational levels of their ground states. Emission properties, in particular thekrrates, are used to demonstrate the existence of radiationless coupling between theCtilde; andBtilde; states for both ions. For large vibrational energies in theBtilde;thinsp;2A2ustate of C6F+6,knrincreases quasiexponentially with the internal vibrational energyEvin agreement with results of Maier and Thommen who used a different experimental technique. Below 3100 cmminus;1, we find thatknrno longer depends monotonically onEvand is sensitive to the particular vibrational mode excited in theBtilde; state. Results are given of model calculations of the relativeknrrates as a function of specific vibrational levels of C6F6+in theBtilde; state. The results reproduce our experimentally observed mode selective behavior ofknrin C6F+6. Comparison with experiment shows that with the increasing values ofEvthe excited vibronic state gradually loses its memory of initial mode composition, exhibiting vibrational redistribution to a degree which increases with internal vibrational energy.
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