Resonances in the entrance channel of the F+CH4=>HF+CH3 reaction,

TILL WESTERMAN; JONGJIN B. KIM; MARISSA L. WEICHMAN; CHRISTIAN HOCK; TARA YACOVITCH; JULIANA PALMA; DANIEL N. NEUMARK; UWE MANTHE

Angewandte Chemie

WILEY-V C H VERLAG GMBH

Lugar: Weinheim; Año: 2014 vol. 53 p. 1122 - 1126

1433-7851

Extending the fully quantum state resolved description of elementary chemical reactions beyond three or four atom systems is a crucial issue in fundamental chemical research. Reactions of methane with F, Cl, H or O are key examples that have been studied prominently. In particular, reactive resonances and nonintuitive mode-selective chemistry have been reported in experimental studies for the F + CH4 → HF + CH3 reaction. By studying this reaction by transition state spectroscopy, this joint theoretical and experimental paper provides a clear pictures of resonances in the F + CH4 system. This picture is deduced from high-resolution Slow Electron Velocity-map Imaging (SEVI) spectra and accurate full dimensional (12D) quantum dynamics simulations in the picosecond regime. The unprecedented quantum dynamics simulations are facilitated by the multi-configurational time-dependent Hartree (MCTDH) approach and employ newly developed, highly accurate vibronically and spin-orbit coupled potential energy surfaces. Basedon these simulations, simple pictures are developed explaining the origin of the resonance structures observed.With F + CH4 → HF + CH3 as a benchmark for polyatomic reactions,this work gives a broader implication of how product formation in low-barrier reactions is mediated by the pre-reactive complex. It is found that steering effects resulting from van der Waals complexes which have been reported for smaller systems are also important in more complex polyatomic reactions. Thus, the results of the present work add to the fundamental understanding of chemical reactivity and should be of interest for a general chemistry audience.