β -decay scheme of 140Te to <mml:mmultiscripts>I 140 </mml:mmultiscripts>: Suppression of Gamow-Teller transitions between the neutron h9 /2 and proton h11 /2 partner orbitals

We report for the first time the β -decay scheme of ¹⁴⁰Te (Z =52 ) to ¹⁴⁰I (Z =53 ), with a specific focus on the Gamow-Teller strength along N =87 isotones. These results were obtained in an experiment performed at the Radioactive Ion Beam Factory (RIBF), RIKEN, where the parent nuclide, ¹⁴⁰Te, was produced through the in-flight fission of a ²³⁸U beam at 345 MeV per nucleon impinging on a ⁹Be target. Based on data from the high-efficiency γ -ray spectrometer, EUROBALL-RIKEN Cluster Array (EURICA), we constructed a decay scheme of ¹⁴⁰I. The half-life of ¹⁴⁰Te has been determined to be 350(5) ms. A level at 926 keV has been assigned as a (1⁺) state based on the logf t value of 4.89(6). This (1⁺) state, commonly observed in odd-odd nuclei, can be interpreted in terms of the π h_{11 /2}ν h_{9 /2} configuration formed by the Gamow-Teller transition between a neutron in the h_{9 /2} orbital and a proton in the h_{11 /2} orbital. We observe a sharp contrast to this type of β -decay branching to the lower-lying 1⁺ states between ¹⁴⁰I and ¹³⁶I, where we see a large reduction as the number of neutrons increases. This is in contrast to the prediction by large-scale shell model calculations. To investigate this type of the suppression, results of the Nilsson model calculations will be discussed. Along the isotones with N =87 , we discuss a characteristic feature of the Gamow-Teller distributions at 1⁺ states with respect to the isospin difference.