Spectroscopy of the transition state: hydrogen abstraction reactions of fluorine

Abstract

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.

Proton transfer dynamics on highly attractive potential energy surfaces: Induced repulsive energy release in O− + HF at high collision energies

“…2 and 3 have peaks at 0" and 180" in center-of-mass coordinates, showing clear symmetry about 90". Flux distributions with this symmetry are generally diagnostic of the decay of a transient complex living at least several rotational periods (25,26), supporting calculations that predict the existence of an 0-.HF complex stable relative to 0-+ HF by 187 kJ mol-I (22). In the decay of such a transient complex, the products "forget" the direction of initial reagent approach and the energy distributions are independent of scattering angle.…”

“…Those studies showed that, relative to the thermal energy reference data, incremental translation appears to be partitioned preferentially into product vibration. Knutsen et al have interpreted these observations as a consequence of the attractive well on the potential surface, estimated from ab initio calculations to be 187 kJ mol-' relative to the reagents (22). The drift tube ex~eriments showed that the fraction of the total available energy appearing in product vibration increases linearly with increasing translation up to 15 kJ mol-I, consistent with mixed energy release on the Heavy + Light-Heavy potential energy surface.…”

Time‐dependent quantum study of H(2S) + FO(2Π) → OH(2Π) + F(2P) reaction on the 13A′ and 13A″ states

“…Recently, global potential energy surfaces for several electronic states of OHF have been reported. Gómez-Carrasco et al 5 performed high-level MRCI electronic structure calculations for 8069 energy points to calibrate the fitted potential energy surface (PES) of the ground adiabatic 1 3 A triplet electronic state. Quasi-classical trajectory (QCT) and wave packet studies [5][6][7] of F( 2 P) + OH( 2 ) → O( 3 P) + HF( 1 + ) reaction have been performed on this high-quality triplet PES and a subsequent improved version.…”

“…Recently, the reverse reaction, H( 2 S) + FO( 2 ) → OH( 2 ) + F( 2 P) has been subject to many studies. Gogtas 9 has carried out the quantum real wave packet calculations of the reverse reaction on the ground 3 A potential energy surface. The same reaction has been studied by Zhao et al 10 by using QCT method.…”

“…reaction by wave packet calculations implemented with the centrifugal sudden (CS) approximation on the excited 2 3 A and 1 3 A triplet states. Later, the PESs 14 for the first five singlet states of the OHF system have been constructed from ab initio electronic structure calculations at the MRCI level.…”