Pygmy dipole resonance in 124 Sn populated by inelastic scattering of 17 O

1−and2+discrete states inZr90populated via theCrespi1, Bracco2, Nicolini3 et al. 2015Phys. Rev. CSelf Cite361120View full textAdd to dashboardCite

“…The inelastic scattering of 17 O ions at bombarding energy of 20 MeV/u was measured recently to study pygmy states in the 208 Pb [14] and 124 Sn [15] nuclei. Previously, the same reaction was used at 22 MeV/u to study the γ decay of the isoscalar giant quadrupole resonance (ISGQR) of 208 Pb [19] and at 84 MeV/u [20,21] to study giant resonances, in particular the giant dipole resonance (GDR), in 208 Pb, 120 Sn, 90 Zr, and 60 Ni.…”

“…In this connection extensive work [8][9][10][11][12][13] was made using the (α,α ) reaction, having a strong isoscalar character, and the general result is the presence of different excitation pattern as compared with that of the (γ,γ ) reaction. More recently, experiments performed for the nuclei 208 Pb [14], 124 Sn [15], and 140 Ce [16] to study the E1 and E2 transitions in the region 4-9 MeV have shown that the ( 17 O, 17 O γ ) reaction is a good tool to investigate the isospin properties of these states. Indeed, this reaction enhances the excitation of the isoscalar component of states populated with it.…”

Pygmy dipole resonance inCe140via inelastic scattering ofO17

“…The two experiments used the same experimen-tal set up. The measured ISEWSR in the pygmy region for the 124 Sn case in the discrete peaks (low-energy region) was 2.2(±0.3)% and for the whole energy region (including the unresolved region) -7.8(±0.7)% [15]. The ratio of the ISEWSR for 124 Sn and 140 Ce is therefore 2.2%/0.44% = 5 for the discrete peaks.…”

“…Its major part is exhausted by the Isovector Giant Dipole Resonance (IVGDR) (for the overview on giant resonances see Refs. [1,2]), which is a very well studied collective phenomenon described as an out-of-phase oscillation of protons versus neutrons, located in the energy interval well above the neutron separation energy (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Below the IVGDR and around the particle separation energy, a small fraction of fragmented dipole states is also observed, exhausting a few percent of an energy-weighted sum rule (EWSR) depending on the nucleus.…”

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.…”