title: Nuclear deformation and neutron excess as competing effects for dipole strength in the pygmy region.
abstract: The electromagnetic dipole strength below the neutron-separation energy has been studied for the xenon isotopes with mass numbers A=124, 128, 132, and 134 in nuclear resonance fluorescence experiments using the γELBE bremsstrahlung facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIγS facility at Triangle Universities Nuclear Laboratory Durham. The systematic study gained new information about the influence of the neutron excess as well as of nuclear deformation on the strength in the region of the pygmy dipole resonance. The results are compared with those obtained for the chain of molybdenum isotopes and with predictions of a random-phase approximation in a deformed basis. It turned out that the effect of nuclear deformation plays a minor role compared with the one caused by neutron excess. A global parametrization of the strength in terms of neutron and proton numbers allowed us to derive a formula capable of predicting the summed E1 strengths in the pygmy region for a wide mass range of nuclides.
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Massarczyk
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Schwengner
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Dönau
authors.affiliation: University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: S
authors.initials: S
authors.lastname: Frauendorf
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Anders
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Bemmerer
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Beyer
authors.affiliation: Duke University, Durham, North Carolina 27708, USA and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA.
authors.forename: C
authors.initials: C
authors.lastname: Bhatia
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Birgersson
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Martin-Luther Universität Halle-Wittenberg, 06099 Halle, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Butterling
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: Z
authors.initials: Z
authors.lastname: Elekes
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Ferrari
authors.affiliation: Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA and North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Gooden
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Hannaske
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: A R
authors.initials: AR
authors.lastname: Junghans
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Kempe
authors.affiliation: Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA and North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Kelley
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Kögler
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Matic
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: M L
authors.initials: ML
authors.lastname: Menzel
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Müller
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: T P
authors.initials: TP
authors.lastname: Reinhardt
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Röder
authors.affiliation: Duke University, Durham, North Carolina 27708, USA and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA.
authors.forename: G
authors.initials: G
authors.lastname: Rusev
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: K D
authors.initials: KD
authors.lastname: Schilling
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Schmidt
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schramm
authors.affiliation: Duke University, Durham, North Carolina 27708, USA and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA.
authors.forename: A P
authors.initials: AP
authors.lastname: Tonchev
authors.affiliation: Duke University, Durham, North Carolina 27708, USA and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA.
authors.forename: W
authors.initials: W
authors.lastname: Tornow
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Wagner