Point defects in neutron-irradiated MoO3 studied by 99Mo(β−)99Tc perturbed angular correlation Original Research Article

The nuclear quadrupole interaction of 99Mo(β−)99Tc in MoO3 powder subjected to thermal neutron doses up to 6.6 × 1017 n cm−2 was measured at room temperature by time differential perturbed angular correlation. MoO3, sublimed after irradiation, served as a defect-free reference with hyperfine parameters vQ = 154(3) MHz and asymmetry parameter η = 0.59(2). A well-defined defect signal with vQ = 304(4) MHz and η = 1 was observed with relative fractions up to 20% which is attributed to oxygen vacancy formation, very likely created by the Mo recoil during prompt γ-deexcitation after thermal neutron capture.