Lifetime analysis of Te128,130 via the Doppler-shift attenuation method

Abstract

Background: The $Z=52$ nuclei $^{128}\mathrm{Te}$ and $^{130}\mathrm{Te}$ are interesting candidates to study nuclear-structure properties close to the $Z=50$ shell. The knowledge of lifetimes of low-lying states in those nuclei is still scarce.Purpose: The goal of the present work is to extend the experimental database of nuclear level lifetimes of low-spin states in $^{128}\mathrm{Te}$ and $^{130}\mathrm{Te}$.Methods: Nuclear level lifetimes were determined by means of the Doppler-shift attenuation method (DSAM) using $p\ensuremath{-}\ensuremath{\gamma}$ coincidences measured at the SONIC@HORUS setup located at the FN-Tandem ion accelerator of the University of Cologne.Results: For $^{128}\mathrm{Te}$, lifetimes of eleven excited states could be determined, one of these for the first time. For the case of $^{130}\mathrm{Te}$, 18 nuclear level lifetimes were obtained, 15 for the first time. In both experiments, upper limits for lifetimes of several additional levels were determined. Moreover, the nuclear level scheme of $^{130}\mathrm{Te}$ could be extended. One additional level and 13 new transitions for levels above 2.7 MeV have been added. A standard shell-model calculation was performed and compared with the experimental results, showing an overall agreement.Conclusions: DSAM using $p\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences is a powerful tool to determine lifetimes in the subpicosecond range free of feeding contributions. Although both experiments yielded low statistics, numerous lifetimes could be obtained. The use of $p\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences furthermore enables the extension of level schemes.