title: S0 ring-puckering potential energy function for coumaran.
abstract: With the aid of a reported inversion splitting value, the far-infrared spectrum resulting from the ring-puckering vibration of coumaran has been reassigned and the one-dimensional potential energy function has been determined. The barrier to planarity is 155 +/- 4 cm(-1) and the dihedral angle is 25 degrees . These results agree well with the millimeter wave spectra values of 152 cm(-1) and 23 degrees , which utilized different data and a different type of potential function for the calculations. The MP2/cc-pvtz ab initio values of 238 cm(-1) and 26.5 degrees agree more poorly. If the benzene ring is assumed to remain rigid, the calculated barrier drops to 204 cm(-1). The puckering potential functions for the ring-flapping and ring-twisting vibrationally excited states were also determined and the barriers were found to be 149 and 156 cm(-1), respectively.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Yang
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Okuyama
authors.forename: Kevin
authors.initials: K
authors.lastname: Morris
authors.forename: Zane
authors.initials: Z
authors.lastname: Arp
authors.forename: Jaan
authors.initials: J
authors.lastname: Laane