High-spin spectroscopy in 207At: Evidence of a 29/2+isomeric state

Yrast and near-yrast states above the known 25/2+ isomer in 207At are established for the first time. The level scheme is extended up to 47/2 h over bar and 6.5 MeV with the addition of about 60 new gamma-ray transitions. The half-life of the 25/2+ isomer is revisited and a value of T1/2 = 107.5(9) ns is deduced. Evidence of a hitherto unobserved 29/2+ isomer in 207At is presented. A systematic study of B(E3) values for the transitions deexciting the 29/2+ isomer in the neighboring odd -A At isotopes suggests a half-life in the 2-4.5 mu s range for this state in 207At. The experimental results are compared with large-scale shell-model calculations performed using the KHM3Y effective interaction in the Z = 50-126, N = 82-184 model space and an overall good agreement is noted between the theory and the experiment. A qualitative comparison of the excited states and the isomers with analogous states in neighboring nuclei provides further insight into the structure of 207At.

Automated summary

For the first time, Yrast and near-yrast states above the known 25/2+ isomer in 207At are observed. The level scheme is expanded with the addition of around 60 new gamma-ray transitions, reaching up to 47/2 h over bar and 6.5 MeV. The half-life of the 25/2+ isomer is revisited and determined to be 107.5(9) ns. Evidence of a previously unobserved 29/2+ isomer in 207At is presented. B(E3) values for transitions deexciting the 29/2+ isomer in neighboring odd-A At isotopes suggest a half-life in the range of 2-4.5 mu s for this state in 207At. Good agreement is found between experimental results and large-scale shell model calculations using the KHM3Y effective interaction.