The fluorescence lifetimes of single rotational states in the 8(1), 7(1) and 5(1) vibrational levels of the (B) over tilde (2)A " electronic state in jet-cooled vinery radicals have been investigated following coherent excitation. The emission decays were found to be exponential and independent of the rotational quantum number J, and the observed quantum beats were due exclusively to hyperfine interactions. The dynamics of two regimes of radiationless processes (internal conversion with and without curve crossing) were explored and the electronic structure of the (B) over tilde (2)A " state further characterised.