Recent measurements of B(E2) values in even-even Te isotopes have revealed a smooth evolution of quadrupole collectivity, with only a slight asymmetry across the middle of the shell. These findings confirm that the only nucleus exhibiting an "anomalous" B4/2 ratio (B4/2 G 1) in even-even Te isotopes is 114Te. To further investigate this anomaly, lifetime measurements were carried out in the odd-mass isotope 115Te (N = 63), focusing on the 15/2- and 19/2- negative-parity levels in the nu h11/2 band, which are the analog states of the 2+ and 4+ levels in neighboring even-even nuclei. The extracted B(E2) values for 115Te indicate a "normal" behavior, with a B4/2 ratio greater than unity, further restricting the extent of the anomalous region in Te isotopes with B4/2 G 1 to the lower mass region with A G 114. The results have been interpreted using multiple theoretical frameworks: the shell model with the realistic pairing plus multipole terms with monopole interaction, large-scale configuration-interaction shell-model calculations, and the interacting boson-fermion model with triaxial deformation. The models give a fair reproduction of the experimental data, but fail to capture the detailed trend in the case of the B4/2 values.
QC 20260520