title: Femtosecond degenerate four-wave mixing of cyclopropane.
abstract: Femtosecond degenerate four-wave mixing (fs-DFWM) is applied for the measurement of rotational constants of cyclopropane (C3H6). The rotational coherence method yields a very accurate B0 = 20,093.322(12) MHz and centrifugal distortion constants D(J) and D(JK). To exploit the full resolution of the fs-DFWM method, the accuracy of the optical delay measurement was increased by nearly two orders of magnitude, including elimination of effects from the refractive index of air. The fs-DFWM molecular constants are comparable in accuracy to those from high-resolution infrared spectroscopy and are only surpassed by those of dipole distortion microwave spectroscopy. In parallel, the equilibrium structure, vibrationally averaged structure parameters and rotational constants were calculated using high-level ab initio methods and large basis sets. Combining these with the results of previous calculations and the measured rotational constants yields r(e)(C-C) = 1.5034(3) A, r(e)(C-H) = 1.0775(5) A, and alpha(e)(H-C-H) = 115.09(10) degrees.
authors.affiliation: Departement für Chemie und Biochemie, Universität Bern, Switzerland.
authors.forename: Dominique S
authors.initials: DS
authors.lastname: Kummli
authors.forename: Hans M
authors.initials: HM
authors.lastname: Frey
authors.forename: Michael
authors.initials: M
authors.lastname: Keller
authors.forename: Samuel
authors.initials: S
authors.lastname: Leutwyler