The transition-state region for neutral hydrogen-transfer reactions can be probed by photodetaching the appropriate stable, hydrogen-bonded negative ion. This paper presents a detailed account of this method, in which the CI + HCI and Br + HBr reactions are investigated by photoelectron spectroscopy of CIHCI-, BrHBr-, and the corresponding deuterated species. The photoelectron spectra exhibit resolved vibrational structure attributed to the unstable neutral [CIHCI] or [BrHBr] complex. The peaks in the spectra are assigned to the antisymmetric stretch mode of the complex, and the peak widths are sensitive to the lifetime of the complex. The BrHBr-and BrDBr-spectra exhibit narrow (15-20 meV) peaks that are likely to result from reactive resonance states supported by the Br + HBr potential energy surface, as well as peaks that appear to be from an electronically excited state of the [BrHBr] complex. The BrHBr-and BrDBr-results have been analyzed to yield an "effective" collinear potential energy surface for the Br + HBr reaction. (24) Truhlar, D. G.; Kuppermann, A. J. Chem. Phys. 1970,52,384. Wu, (25) Bondi, D. K.; Connor, J. N. L.; Manz, J.; Romelt, J. Mol. Phys. 1983, (26) Manz, J.; Meyer, R.; Schor, H. H. R. (28) Neumark, D. M.; Wodtke, A. M.; Robinson, G . N.; Hayden, C. C.; S.-F.; Levine, R. D. Mol. Phys. 1971, 22, 991. 50, 467. Lee. Y . T. J. Chem. Phvs. 1985. 82. 3045. ~~ (29) Metz, R. B.; Kikopoulos; T.;~Weaver, A.; Neumark, D. M.

The reactions F + CH3OH -HF + CH30, F + C2H5OH -HF + C2H50, and F + OH -HF + 0(3P,'D) are studied by photoelectron spectroscopy of the negative ions CH3OHF~, C2H5OHP, and OHP. In each case, photodetachment accesses the transition-state region for direct hydrogen abstraction. The photoelectron spectra exhibit resolved vibrational structure which is sensitive to details of the potential surface in the transition-state region. To aid in the interpretation of the spectra, ab initio equilibrium structures, harmonic frequencies, and hydrogen bond dissociation energies are calculated for the ions CH3OHP and OHP. The anharmonic hydroxyl hydrogen stretching potential is also calculated for the two ions. Using the calculated ion properties and the fitted ab initio reaction surfaces of Sloan et al. (J. Chem. Phys. 1981, 75, 1190, a two-dimensional dynamical simulation of the photoelectron spectrum of OHP is presented and modifications to the reaction surfaces are discussed. The spectra of the alcohol complexes are discussed in light of this simulation, and the role of the "bath" degrees of freedom in these spectra is considered.

Articles you may be interested inThe electronic states of 1,2,3-triazole studied by vacuum ultraviolet photoabsorption and ultraviolet photoelectron spectroscopy, and a comparison with ab initio configuration interaction methods J. Chem. Phys. 134, 084309 (2011); 10.1063/1.3549812Ultraviolet photoelectron spectroscopy of poly(pyridine2,5diyl), poly(2,2′bipyridine5,5′diyl), and their K doped statesThe photoelectron spectrum of the NO,-anion has been obtained at 266 and at 213 nm. The 266 nm spectrum probes the 2 A ~ ground state of N0 3 • The 213 nm spectrum represents the first observation of the 2 E II lowest-lying excited state of N0 3 • The 2A ~ band shows vibrational progressions in the VI symmetric stretch and the V4 degenerate in-plane bend ofN0 3 • Our analysis of this band indicates that the N0 3 ground state has a D3h equilibrium geometry and is vibronically coupled to the 2 E' second excited state via the v 4 mode. We also obtain the electron affinity ofN0 3 , 3.937 ± 0.014 eV, and the heat off ormation ofN0 3 at 298 K, 0.777 ± 0.027 eV (17.9 ± 0.6 kcaVmol). The 2E" state ofN0 3 lies 0.868 ± 0.014 eV above the ground state. The 2 E" band shows complex and extensive vibrational structure. Several possible assignments of this structure are discussed.

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Angle resolved photoelectron study of resonances near the Si2p edge of the Si(CH3)4 molecule