M. Grinberg

Boson forbidden low-energy E1-transitions in spherical nuclei

Low-energy E1-transitions in spherical nuclei forbidden in the ideal boson picture are considered. For that the internal fermion structure of nuclear excitations is taken into account. Several examples of such transitions calculated within the Quasiparticle Phonon Model are considered and the role of dipole core polarization is discussed. It is shown that transition probabilities of an order of 10 3 W.u. observed experimentally are well described by this model. c 1998 Elsevier Science B.V.

Two-phonon J = 1 states in even-mass Te isotopes with A = 122–130☆

Abstract Excited states of the nuclei 122,126,130 Te were populated via the (γ, γ′) reaction at endpoint energies of the bremsstrahlung between 4.5 and 5.5 MeV. Gamma rays were detected with a EUROBALL CLUSTER detector and a single HPGe detector. In all investigated nuclei two or three prominent dipole transitions were identified at E γ ≈ 3 MeV. The corresponding low-lying J = 1 states are interpreted as two-phonon excitations. Quasiparticle-phonon-model calculations predict at about 3 MeV one 1 − state arising from the coupling of the first quadrupole and the first octupole phonon, and one 1 + state arising from the coupling of the first and the second quadrupole phonon, where the latter has isovector character. Such an excitation mode can be considered as an analogue of the scissors mode in vibrational nuclei. The calculated transition strengths are compatible with experimental ones within a factor of about 1.5.

The nuclear structure of 126Te studied with (d,p), (d,3He) and (d,d′) reactions☆

Abstract At the Munich Tandem Accelerator the reactions 125 Te(d, p) 126 Te, 126 Te(d, d′) 126 Te and 127 I(d, 3 He) 126 Te were measured with deuteron energies between 24 and 28 MeV up to excitation energies of about 3.2 MeV. Using γ-lines from previous (n,γ), (n,n′γ) and (γ,γ′) experiments, a level scheme of 126 Te up to above 3 MeV was established. The results are compared with quasiparticle-phonon model calculations.

Study of 122Te with charged particle reactions

Abstract The reactions 122 Te(d,d′) 122 Te, 123 Te(d,t) 122 Te, 123 Te( 3 He, 4 He) 122 Te, and 121 Sb( 3 He,d) 122 Te were measured with the Q3D magnetic spectrograph of the Munich Tandem Accelerator. The level scheme of 122 Te was extended up to about 4 MeV using also previous results and new 122 Te(γ,γ′) 122 Te data. The level scheme is compared with IBA and QPM calculations. An intruder band is proposed with the 0 + band head at 1746 keV.

High-spin states of 8838Sr50: breaking of the neutron core

Abstract The nucleus 88 Sr has been produced at high spin as fission fragment following the fusion reaction 28 Si + 176 Yb at 145 MeV bombarding energy. The γ -rays were detected with the Eurogam2 array. The level scheme of 88 Sr has been extended up to 8.5 MeV excitation energy and spin values around 14ℏ. The structure of the high-energy states is discussed by analogy with those of the even–even neighbouring N =50 isotones and possible configurations are proposed. They are compared with results obtained within the Quasiparticle-Phonon Model.

Structure of the146Sm states from the146Eu decay

The146Eu→146Sm decay is studied using theγ-ray anti-Compton spectrometer. The decay scheme is constructed. It contains 68 levels. Spins, parities and log ft values of the excited levels of146Sm are determined. Calculations within the framework of the interacting boson model and of the quasiparticle phonon model are presented.

The influence of the GDR on the low-energy E1 transitions in spherical nuclei

Abstract Low-energy E1-transitions in spherical nuclei forbidden in the ideal boson picture are considered. For that the internal fermion structure of nuclear excitations is taken into account. Several examples of such transitions calculated within the Quasiparticle Phonon Model are considered and the role of dipole core polarization is discussed.

Properties of the low-lying excited states in even-even nuclei around the closed shell N=82

The properties of low-lying states in 136Ba and 144Nd are calculated within the quasiparticle phonon model. It is shown that the strong quadrupole interaction in the particle-particle channel leads to the appearance of low-lying isovector excitations. Due to this reason, there are two branches in the lowlying part of the spectrum, an isoscalar and an isovector one. Both branches show peculiar regularities of E2 and M1 transitions.