Strong quantum coupling between O-H+-O stretch and flanking group motions in (CH3OH)2H+ Part II: Tuning the coupling via isotopologues

Abstract

The vibrational coupling between O-H$^{+}$-O/O-D$^{+}$-O stretch and flanking group motions were explored in the following isotopologues: \chem{(CH_3OH)_2H^+}, \chem{(CD_3OH)_2H^+}, \chem{(CH_3OD)_2D^+}, and \chem{(CD_3OD)_2D^+}. At present only measurements for \chem{(CH_3OH)_2H^+} are available in the literature.\footnote{J.R. Roscioli, L.R. McCunn and M.A. Johnson. Science 2007, 316, 249}$^{-}$ \footnote{T.D. Fridgen, L. Macaleese, T.B McMahon, J. Lemaire and P. Maitre. Phys. Chem. Chem. Phys. 2006, 8, 955-966} Reduced-dimensional calculations were performed by solving several vibrational Schrödinger equations using the method of Discrete Variable Representation (DVR) with harmonic oscillator as basis. Both potential and dipole moment surfaces were constructed at MP2/aug-cc-pVDZ by scanning along normal modes corresponding to: 1) O-H$^{+}$-O/O-D$^{+}$-O stretch, 2) out-of-phase C-O stretch, 3) in-plane \chem{CH_3}/\chem{CD_3} rock, 4) out-of-plane \chem{CH_3}/\chem{CD_3} rock, and 5) O-O stretch. It was found that vibrational states for isotopologues corresponding to O-H$^{+}$-O are more mixed than that of the O-D$^{+}$-O. Lastly, we proposed tentative assignments for the simulated spectrum and hope that experimental measurements will be available in the near future.