title: Communication: Spectroscopic consequences of proton delocalization in OCHCO⁺.
abstract: Even though quartic force fields (QFFs) and highly accurate coupled cluster computations describe the OCHCO(+) cation at equilibrium as a complex between carbon monoxide and the formyl cation, two notable and typical interstellar and atmospheric molecules, the prediction from the present study is that the equilibrium C(∞v) structure is less relevant to observables than the saddle-point D(∞h) structure. This is the conclusion from diffusion Monte Carlo and vibrational self-consistent field/virtual state configuration interaction calculations utilizing a semi-global potential energy surface. These calculations demonstrate that the proton "rattle" motion (ν6) has centrosymmetric delocalization of the proton over the D(∞h) barrier lying only 393.6 cm(-1) above the double-well OCHCO(+) C(∞v) minima. As a result, this molecule will likely appear D∞h, and the rotational spectrum will be significantly dimmer than the computed equilibrium 2.975 D center-of-mass dipole moment indicates. However, the proton transfer fundamental, determined to be at roughly 300 cm(-1), has a very strong intensity. This prediction as well as those of other fundamentals should provide useful guides for laboratory detection of this cation. Finally, it is shown that the two highest energy QFF-determined modes are actually in good agreement with their vibrational configuration interaction counterparts. These high-level quantum chemical methods provide novel insights into this fascinating and potentially common interstellar molecule.
authors: Department of Chemistry, Georgia Southern University, Statesboro, Georgia 30460, USA.
authors: Ryan C
authors: RC
authors: Fortenberry
authors: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA.
authors: Qi
authors: Q
authors: Yu
authors: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA.
authors: John S
authors: JS
authors: Mancini
authors: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA.
authors: Joel M
authors: JM
authors: Bowman
authors: NASA Ames Research Center, Moffett Field, California 94035-1000, USA.
authors: Timothy J
authors: TJ
authors: Lee
authors: Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA.
authors: T Daniel
authors: TD
authors: Crawford
authors: Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138, USA.
authors: William F
authors: WF
authors: Klemperer
authors: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
authors: Joseph S
authors: JS
authors: Francisco