An equilibrium focused approach to calculating the Raman spectrum of the symmetric OH stretch in formic acid dimer

The recent reaction surface Hamiltonian model for the double proton tunneling in formic acid dimer of Barnes et al. G.L. Barnes, S.M. Squires, E.L. Sibert, J. Phys. Chem. B. 112 (2008) 595.] has been applied to the calculation of the symmetric OH stretching Raman spectra. We interpret the full Raman spectra obtained through use of a simplified, single minimum spectrum. Extensive state mixing is found, leading to broad spectral features. Results compare well with the experimental measurements of Bertie et al. J.E. Bertie, K.H. Michaelian, H.H. Eysel, D. Hager, J. Chem. Phys. 85 (9) (1986) 4779]. We also report improvements upon our previous approach and present ground state and fundamental frequencies as well as tunneling splittings obtained with our new method.