Symmetric double proton tunneling in formic acid dimer: A diabatic basis approach

Title Symmetric double proton tunneling in formic acid dimer: A diabatic basis approach
Publication Type Journal Article
Year of Publication 2008
Authors Barnes GL, Squires SM, Sibert, Edwin L. III
Journal Journal of Physical Chemistry B
Volume 112
Pagination 595-603
Date Published Jan
Accession Number ISI:000252287200045
Keywords anion, carboxylic-acid, chemical-reactions, Chemistry, Physical, davidson algorithm, discrete variable representation, excited vibrational-states, ground-state, hydrogenoxalate, polar environment, polyatomic-molecules, raman-spectra
Abstract A model of double proton tunneling in formic acid dimer is developed using a reaction surface Hamiltonian. The surface includes the symmetric OH stretch plus the in-plane stretch and bend interdimer vibrations. The surface Hamiltonian is coupled to a bath of five A,, and B-3g normal modes obtained at the D-2h transition state structure. Eigenstates are calculated using Davidson and block-Davidson iterative methods. Strong mode specific effects are found in the tunneling splittings for the reaction surface, where splittings are enhanced upon excitation of the interdimer bend motion. The results are interpreted within the framework of a diabatic representation of reaction surface modes. The splitting patterns observed for the reaction surface eigenstates are only slightly modified upon coupling to the bath states. Splitting patterns for the bath states are also determined. It is found that predicting these splittings is greatly complicated by subtle mixings with the inter-dimer bend states.
Short Title J. Phys. Chem. B
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