title: Azimuthal reorientation of pentacene upon 2D condensation.
abstract: We report a novel two-dimensional gas-solid phase transition of pentacene molecules on the Cu(110)-(2 × 1)O surface where the 2D condensation is accompanied by a reversible azimuthal rotation of the pentacene molecules. The change of the optical anisotropy associated with this reorientation allows us to explore the 2D condensation as a function of coverage and temperature by reflectance difference spectroscopy. As a result, the 2D heat of condensation of pentacene on Cu(110)-(2 × 1)O is determined to be 84 meV, which is more than one order of magnitude smaller than the respective value for 3D crystallization.
authors.affiliation: Institute of Experimental Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria. lidong.sun@jku.at
authors.forename: L D
authors.initials: LD
authors.lastname: Sun
authors.forename: J
authors.initials: J
authors.lastname: Gall
authors.forename: G
authors.initials: G
authors.lastname: Weidlinger
authors.forename: C Y
authors.initials: CY
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Denk
authors.forename: P
authors.initials: P
authors.lastname: Zeppenfeld