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The short, excited life of tellurium

Lifetime analysis of excited states in the Te midshell region

Time: Wed 2024-04-03 13.00

Location: FB55, Roslagstullsbacken 21, Stockholm

Language: English

Subject area: Physics, Atomic, Subatomic and Astrophysics

Doctoral student: Ebba Ahlgren Cederlöf , Kärnfysik, Uppsala University

Opponent: Associate Professor Matthias Weiszflog, Uppsala University, Department of Physics and Astronomy, Applied Nuclear Physics

Supervisor: Professor Ayse Nyberg, Kärnfysik; Associate Professor Torbjörn Bäck, Kärnfysik; Professor Johan Nyberg, Uppsala University, Department of Physics and Astronomy, Nuclear Physics

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QC 2024-03-15

Abstract

In this licentiate thesis, lifetimes of low lying excited states in the midshell region of tellurium isotopes are discussed. The nuclear lifetimes are interesting properties to study, since they are inversely proportional to the transition probabilities, which contain information on the underlying structure of the nucleus. By measuring the lifetime of a transition, information can be gained on e.g. the collectivity of the state.

The main results presented in this thesis are the lifetime measurements of the 2+ → 0+ and 4+ → 2+ transitions in 118Te described in Paper I. The principal aim of this paper was to reduce the relative uncertainty in the 2+ lifetime, to better see the trend of the 2+ → 0+ transition probabilities over the tellurium isotopic chain.

The work presented in Paper I is based on data from an experiment conducted in 2017 at the JYFL accelerator facility in Jyväskylä, Finland. In this experiment, excited states of were populated in the fusion-evaporation reaction 100Mo(22Ne,4n)118Te at a beam energy of 75 MeV. The lifetimes were extracted using the Recoil Distance Doppler Shift (RDDS) technique, with the Jurogam II γ-ray spectrometer coupled to the Differential Plunger for Unbound Nuclear States (DPUNS). Data analysis was performed using the Differential Decay Curve Method (DDCM) in coincidence mode. The lifetimes were determined to be τ2+ = 7.46(19) ps and τ4+ = 4.25(23) ps, in agreement with previous measurements, but with reduced uncertainty. In the case of the 2+ lifetime, the new result reduces the relative uncertainty of the lifetime from 16% to 2.5%, allowing for more precise tests of theoretical predictions.

In addition to 118Te, an analysis of lifetimes of low-lying excited states in the odd-A nuclei 117Te and 119Te is ongoing and an experiment aiming to measure lifetimes in 116Te has been accepted. These nuclides will also be discussed in this thesis.

urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-344149