title: Microscopic nature of the pygmy dipole resonance: the stable Ca isotopes.
abstract: The electric dipole strength distribution in 44Ca has been measured up to 10 MeV in high resolution photon scattering experiments for the first time. The data obtained have been compared to earlier measurements on (40,48)Ca in order to view the evolution of the electric pygmy dipole resonance (PDR). Calculations that were performed within the framework of the microscopic extended theory of finite Fermi systems, which adds contributions of the quasiparticle-phonon coupling to random phase approximation calculations, give a qualitative agreement with the experimental data for all three isotopes. We have shown that it is necessary to include this coupling to describe the PDR.
authors.affiliation: Institut fỳr Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Hartmann
authors.forename: M
authors.initials: M
authors.lastname: Babilon
authors.forename: S
authors.initials: S
authors.lastname: Kamerdzhiev
authors.forename: E
authors.initials: E
authors.lastname: Litvinova
authors.forename: D
authors.initials: D
authors.lastname: Savran
authors.forename: S
authors.initials: S
authors.lastname: Volz
authors.forename: A
authors.initials: A
authors.lastname: Zilges