The electromagnetic transition probabilities of the yrast 2 + states in the midshell Te isotopes, two protons above the closed shell at Sn, are of great importance for the understanding of nuclear collectivity in these isotopes and the role played by the neutron-proton interactions and cross-shell excitations. However, the large uncertainty of the experimental data for the midshell nucleus 118Te and the missing data for 116Te make it difficult to pin down the general trend of the evolution of transition probabilities as a function of the neutron number. In this work, the lifetime of the yrast 2 + state in 118Te was measured, with the aim of reducing the uncertainty of the previous measurement. The result is τ2 += 7.46 (19) ps. In addition, the lifetime of the 4 + state was measured to be τ4 += 4.25 (23) ps. The experimental transition rates are extracted from the measured lifetimes and compared with systematic large-scale shell-model calculations. The trend of the B(E2 ; 0 +→ 2 +) values in the midshell area is in good agreement with the calculations and the calculated B4 / 2 ratio provide evidence for 118Te as a near perfect harmonic vibrator.

With the recent lifetime measurements of the 2 + states in Te 116 and Te 118 , the evolution of the collectivity in the midshell region of the Te isotopic chain is starting to reveal itself. However, more information on the structure of the ground-state bands and the nature of the collectivity can be gathered from studying the odd-mass systems, in which lifetimes have not been extensively studied.

The purpose of the present work is to investigate the structure of low-lying excited states of the ν h 11 / 2 band in the odd-mass systems Te 117 and Te 119 , that correspond to the ground-state band in even-even Te.

Lifetimes of low-lying states in the ν h 11 / 2 band of Te 117 are measured for the first time and remeasured in Te 119 , using the recoil distance Doppler shift technique, and analyzed with the differential decay curve method in coincidence mode.

The lifetimes and B (E2) values of the first two transitions, 15 / 2 − → 11 / 2 − and 19 / 2 − → 15 / 2 − , in the ν h 11 / 2 band, are determined in both Te 117 and Te 119 . From the lifetimes, the B (E2) values and corresponding B 4 / 2 ratios are determined. The results are compared to systematics in both even- A and odd- A Te isotopes, as well as with theoretical results from the large-scale shell model and interacting boson model calculations.

While the energy levels of Te 117 and Te 119 , similarly to Te 118 , exhibit textbook vibrational behavior, the unexpectedly small B 4 / 2 ratios of these odd-mass nuclei point to a puzzling discrepancy and question the vibrational nature of these states.