The fluorescence depletion spectroscopy of CdCH3

The fluorescence depletion spectroscopy (FDS) technique has been applied to the A 2E electronic state of the CdCH3 radical to investigate “dark” vibronic levels. The observed FDS spectrum complements the sparse laser-induced fluorescence and resonance-enhanced multiphoton ionization spectra. Both the upper and lower spin components of the vibrationless level as well as excitations involving the symmetric modes ν2 and ν3, and the antisymmetric mode ν6, as well as combinations involving these modes, were observed. A combined Jahn-Teller and spin-orbit coupling model was used to explain the vibronic structure in the A 2E electronic state as well as strong variations in the Coriolis coupling constants obtained from the resolved rotational K structure. Lifetimes for fluorescing levels have been determined from their temporal decay and those for some dark levels via lifetime broadening measurements. The selectivity of the radiationless decay channel and its possible attribution to an isomerization process are d...