Collective and two-quasiparticle excitations in128Te

Abstract

Excited levels of 128 Te to 3.3 in MeV excitation have been studied using γ-ray spectroscopy following inelastic scattering of accelerator-produced neutrons. Spectroscopic information, including transition energies, level spins, E2/M1 multipole-mixing ratios, and γ-ray branching ratios, was determined from γ-ray excitation functions measured from E n = 2.15 to 3.33 MeV in 90 keV increments, γ-ray angular distributions measured at E n = 2.2, 2.8, and 3.3 MeV, and γγ coincidences measured at E n = 3.6 MeV. Lifetimes of levels in 128 Te were deduced using Doppler-shift attenuation techniques. Absolute transition probabilities were determined for many levels and compared to interacting boson model and particle-core coupling model calculations to identify few particle and collective structures; states exhibiting the decay characteristics expected for two-phonon, mixed-symmetry, and quadrupole-octupole coupled states are identified.

Emerging nuclear collectivity in 124−130Te

“…The aim of this analysis was to determine the 4 + 1 → 2 + 1 matrix elements, while other matrix elements were allowed to vary where a measurement of the relevant yield was possible. There are a number of previously measured lifetimes of higher excited states and mixing ratios of the transitions between higher excited states [8][9][10][26][27][28][29] which were used to constrain matrix elements that could not be determined in the current experiment. The signs of all matrix elements, including those determined from previously measured lifetimes, were taken to be those predicted by shell-model calculations, as were the matrix elements involving weakly populated states.…”

“…A natural next step in the study of such phenomena is the Coulomb excitation of the Te isotopes, which are closer to the Z=50 shell closure. The Te isotopes lie between the Xe and Sn isotopes and have been investigated previously [8][9][10][11][12][13][14][15] with comparison made to the harmonic vibrational model, however, the transition strengths between the 2 + 1 and 4 + 1 have not previously been reported in 128,130 Te. The previous measurement in 126 Te has a large (∼40%) uncertainty.…”

Dipole response inTe128,130below the neutron threshold

“…The data shown and discussed in this article are tabulated in the Supplemental Material [75] partly using information and decay properties of already known levels from Refs. [76][77][78][79][80].…”

Description of the critical point symmetry in 124 Te by IBM-2

“…Comparison of the calculated M 1 transition strengths (in units of µ 2 N ) and the experimental data for 124 Te. The experimental data are taken from Refs [11,45,46,60]…”