Decay of tungsten-189

We studied the decay of 189W as produced via the 192Os[n,α]189W reaction on a 99.9% isotopically enriched 192Os target. The irradiations were performed at the intense neutron beam facility at Cyclotron Research Center, Université Catholique Louvain-la-Neuve (CRC-UCL) (Belgium), where fast neutrons [Ennot, vert, similar20 MeV, φn=(4.8±0.3)1011 ns−1 cm−2] were generated by stopping 50 MeV deuterons on a thick Be target. The half-life of 189W was determined to be 9.3±0.3 min, compared to 10.8±0.2 min obtained from the 188W[n,γ]189W reaction. The energies of the two predominant γ-rays of 189W, 260.4±1.3 and 421.7±1.4 keV were in good agreement with that from the [n,γ] reaction, however, the relative intensities of the two γ-rays were not consistent. From the [n,γ] reaction, the relative intensities of the 260 and 421 keV γ-rays were 97 to 100, whereas from the [n,α] reaction the relative intensities were 100 to 77, respectively. Assuming a cross-section ratio of 20±5 for [n,p3n] to [n,α] reactions, a cross-section of 0.5±0.2 mb was suggested for the 192Os[n,α]189W reaction, and the absolute intensity of the 260 keV γ-ray was estimated to be not, vert, similar50%.