Fine structure of the E1 response in 140Ce below the particle threshold

Decay of quadrupole-octupole1−states inCa40andCe140Derya1, Tsoneva2, Aumann3 et al. 2016Phys. Rev. CSelf Cite12120View full textAdd to dashboardCite

“…The IVGDR is classically described by a Lorentzian shape [2]. Recently, in nuclei with neutron excess an additional dipole strength component below and around the neutron threshold was found on top of the low-energy tail of the IVGDR [3][4][5][6]. This mode of excitation is usually denoted as pygmy dipole resonance (PDR) because it resembles a resonance-like accumulation of close-lying J π = 1 − states with similar spectroscopic features [6].…”

“…In a simple macroscopic picture, a displacement of center-of-mass and center-ofcharge of the nucleus generates a vibrational motion trying to restore the proton-neutron symmetry. Nowadays, the rapidly increasing number of experiments using different probes and techniques allow for systematic studies of the PDR over isotopic and isotonic chains from different mass regions [4,[7][8][9][10][11][12][13][14][15][16][17]. A close connection between * derya@ikp.uni-koeln.de the total PDR strength and the amount of the neutron excess of neutron-rich nuclei which on the other hand is correlated with the neutron skin thickness was proposed [6,[18][19][20].…”

Gamma Decay of the Possible $1^-$ Two-phonon State in $^{140}$Ce Excited via Inelastic Scattering of $^{17}$O

“…This shift in energy is an indication of anharmonicity which is due to the coupling among states of one-, two-and three-phonon states [2]. Experiments using the Nuclear Resonance Fluorescence (NRF) have not found in the 140 Ce the γ transitions to the one-phonon constituents [3,4] It has been demonstrated [6] that the inelastic scattering of 17 O at the energy of 20 MeV/u successfully populates the dipole states below the particle emission threshold, the so-called pygmy dipole resonance (PDR), for a few nuclei: 90 Zr [7], 124 Sn [8], 140 Ce [9], 208 Pb [10]. As discussed above, the lowest lying dipole state in 140 Ce is considered to have a two-phonon character.…”

Decay pattern of the Pygmy Dipole Resonance in140Ce

“…The properties of this phenomenon have been studied in stable (see e.g. [3][4][5][6][7][8][9][10][11]) and in a few radioactive nuclei [12][13][14], in particular in the Z=50 and N=82 mass region. The underlying nature of the PDR is still unclear, and strong experimental and theoretical effort is put into its investigation.…”