title: Ground and asymmetric CO-stretch excited state tunneling splittings in the formic acid dimer.
abstract: There has been some controversy concerning the assignment of measured tunneling splittings for the formic acid dimer in the vibrational ground state and the asymmetric CO-stretching excited state. The discussion is intimately related to the question whether the fundamental excitation of the CO-vibration promotes or hinders tunneling. Here we will address this issue on the basis of a five-dimensional reaction space Hamiltonian which includes three large amplitude coordinates as well as two harmonic modes whose linear superposition reproduces the asymmetric CO-vibrational mode. Within density functional theory using the B3LYP functional together with a 6-311++G(3df,3pd) basis set we obtain a ground state tunneling splitting which is about 2.4 larger than the one for the CO-stretching excited state.
authors.affiliation: Department of Physical Chemistry, Rudjer Bosković Institute, 10000 Zagreb, Croatia.
authors.forename: I
authors.initials: I
authors.lastname: Matanović
authors.forename: N
authors.initials: N
authors.lastname: Doslić
authors.forename: O
authors.initials: O
authors.lastname: Kühn