title: Progress on inner-shell excitations of molecular van der Waals clusters.
abstract: Recent progress on core-level excitation of molecular van der Waals clusters is reported. Resonant excitation near element K edges of isolated and clustered molecules gives rise to small spectral shifts that can only be detected with high spectral resolution. This requires the use of state-of-the-art storage-ring facilities along with insertion devices and high-resolution soft X-ray monochromators. Selected experimental results on carbon monoxide clusters are reported. For the vibrationally resolved C 1s --> pi* (v = 0) band of clustered CO, these indicate characteristic line broadening as well as a small red shift of 2 +/- 1 meV compared with the isolated molecule. The results are discussed within the framework of the quasi-atomic approach with respect to intermolecular interactions, freezing of molecular rotations in clusters, and dynamic localization of resonant core-to-valence excitations.
authors.affiliation: Fachbereich Physik, Universität Osnabrück, Germany. ruehl@uos.de
authors.forename: E
authors.initials: E
authors.lastname: Rühl
authors.forename: R
authors.initials: R
authors.lastname: Flesch
authors.forename: W
authors.initials: W
authors.lastname: Tappe
authors.forename: A A
authors.initials: AA
authors.lastname: Pavlychev