Search for the electric dipole excitations to the3s1/2⊗[21+⊗

Abstract

The odd-mass 117 Sn nucleus was investigated in nuclear resonance fluorescence experiments up to an end point energy of the incident photon spectrum of 4.1 MeV at the bremsstrahlung facility of the Stuttgart University. More than 50 mainly hitherto unknown levels were found. From the measurement of the scattering cross sections model independent absolute excitation strengths were extracted. The measured angular distributions suggested the spins of 11 excited levels. Quasiparticle phonon model calculations including a complete configuration space were performed for the first time for a heavy odd-mass spherical nucleus. These calculations give a clear insight in the fragmentation and distribution of the E1, M 1, and E2 excitation strength in the low energy region. It is proven that the 1 Ϫ component of the two-phonon ͓2 1 ϩ 3 1 Ϫ ͔ quintuplet built on top of the 1/2 ϩ ground state is strongly fragmented. The theoretical calculations are consistent with the experimental data.

Interweaving of elementary modes of excitation in superfluid nuclei through particle-vibration coupling: Quantitative account of the variety of nuclear structure observables

“…3 display similarity with those of Ref. [44], solely dedicated to a γ -decay study of 117 Sn and carried out making use of the quasiparticle phonon model.…”

Extended theory of finite Fermi systems: collective vibrations in closed shell nuclei

“…Unprecedentedly high resolution and high efficiency of detecting gamma rays with energies up to 20 MeV have already given new and very precise information, not only on deformed nuclei, but also on low-lying levels in odd and even-even spherical nuclei. In fact, these detectors give direct information about the low-lying complex configurations containing phonons [58,59,60,61,62], which may be seen again in the fine structure of the giant resonances. At last, in order to explain the large amount of available data on the decay properties of GMR's gained in experiments with coincidences of secondary particles [52,30] it is also necessary to take complex configurations into account (see, for example, refs.…”

Dipole strength distributions of the stable odd-massN=82isotonesLa139andScheck1, Brentano2, Fransen3 et al. 2007Phys. Rev. CSelf Cite

“…Since then, similar examples have been observed in many odd-mass nuclei in the vicinity of the Z = 50 proton shell closure ( 115 In [27], 117 Sn [28], 121 Sb and 123 Sb [29]) and near the N = 82 neutron shell closure, 135,137 Ba [20] and 133 Cs [30]. Except for 123 Sb, 133 Cs, and 137 Ba, all of these nuclei exhibited E1 strength comparable to that observed for the 1 − states in their neighboring even-even core nuclei.…”