Stimulated emission pumping spectra and intramolecular vibrational dynamics of DFCO(S-0) from 9000 to 20,000 cm(-1)

Dispersed fluorescence (DF) and stimulated emission pumping (SEP) spectra o f DFCO from 9000 to 20000 cm(-1) on S-0 are reported. Groups of features in the 2(1)5(1)6(2) DF spectrum are assigned as strongly coupled members of 2 66 [nu(2)(CO stretch) <-> 2 nu(6)(out-of-plane bend)] polyads of vibrationa l states. The Franck-Condon active states in these polyads are primarily th e zero-order states 2(n)6(m) with values of n ranging from 0 to 4 and value s of n2 ranging from 13 to 19. The assignment of the Franck-Condon active s tates is consistent with the HFCO experimental results and with Franck-Cond on factor calculations. Multiple intramolecular vibrational energy redistri bution (IVR) time scales are evident from the dilution of the Franck-Condon factors observed in the spectra examined at different resolutions. The fas test IVR results from the low-order (Delta upsilon = 3) 266 resonance that couples nu(2) and nu(6). This initial IVR occurs in similar to 25 fs. Evide nce of anharmonic coupling within the vicinity of single DF features signif ies subsequent IVR on the 0.5-4.0 ps time scale. This second time scale can be understood in terms of further coupling to nu(3) (HCO bend) and nu(5) ( FCO bend) resulting from a 3566 Darling-Dennison resonance. Clumps of vibra tional lines within individual SEP bands indicate further anharmonic and we ak A-type Coriolis coupling to background levels at times between 3 and 150 ps. Comparison of the observed and calculated vibrational-state densities indicates that, for many states, IVR may be nearly complete on the time sca le of the measured dissociation rates. The IVR dynamics of DFCO are in mark ed contrast to the mode-specific IVR dynamics of HFCO. The quasistability o f extreme-motion out-of-plane vibrations (upsilon(6) greater than or equal to 14), in HFCO is destroyed by the strong coupling of nu(2) and 2 nu(6) in DFCO. Thus, the two isotopomers display qualitatively different IVR dynami cs.