title: Origin of low-energy quadrupole collectivity in vibrational nuclei.
abstract: The coupling of the giant quadrupole resonance to valence-space configurations is shown to be the origin of the formation of low-lying quadrupole-collective structures in vibrational nuclei with symmetric and mixed-symmetric character with respect to the proton-neutron degree of freedom. For the first time experimental evidence for this picture is obtained from electron- and proton scattering experiments on the nucleus ^{92}Zr that are sensitive to the relative phase of valence-space amplitudes by quantum interference.
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Walz
authors.forename: H
authors.initials: H
authors.lastname: Fujita
authors.forename: A
authors.initials: A
authors.lastname: Krugmann
authors.forename: P
authors.initials: P
authors.lastname: von Neumann-Cosel
authors.forename: N
authors.initials: N
authors.lastname: Pietralla
authors.forename: V Yu
authors.initials: VY
authors.lastname: Ponomarev
authors.forename: A
authors.initials: A
authors.lastname: Scheikh-Obeid
authors.forename: J
authors.initials: J
authors.lastname: Wambach