Positron–K-Electron Annihilation in 180mTa Atoms

The excitation cross sections of 180mTa are measured for the first time via positron–K-electron annihilation with a limit energy of 0.653 MeV. Effective cross sections σeff (180gTa) are found to be (3.9 ± 0.8) × 10−29 cm2. The differential cross section is estimated from the effective cross section and agrees qualitatively with theoretical calculations for E1 transitions.