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Decay of tungsten-189
S Mirzadeh1, F Y Lambrecht, R M Lambrecht
1Nuclear Science and Technology Division, Oak Ridge National Laboratory, TN 37831-6229, USA. mirzadehs@ornl.gov
Summary
This study determined the half-life of 189W to be 9.3 minutes using the 192Os[n,alpha]189W reaction, with gamma-ray intensities differing from the 188W[n,gamma]189W reaction. Further analysis suggests a cross-section for the 192Os[n,alpha]189W reaction.
Area of Science:
- Nuclear Physics
- Nuclear Reactions
- Radioactive Decay
Background:
- Investigating the decay properties of Tungsten-189 (189W) is crucial for understanding nuclear structure and reaction mechanisms.
- Previous studies have reported differing half-life values for 189W, necessitating further experimental verification.
Purpose of the Study:
- To accurately determine the half-life of 189W produced via the 192Os[n,alpha]189W reaction.
- To compare the decay characteristics, including gamma-ray energies and relative intensities, with those obtained from the 188W[n,gamma]189W reaction.
- To estimate the cross-section for the 192Os[n,alpha]189W reaction.
Main Methods:
- Irradiation of a 99.9% isotopically enriched 192Os target using fast neutrons (approx. 20 MeV) generated at the Cyclotron Research Center, Université Catholique Louvain-la-Neuve.
- Measurement of the decay of 189W, determining its half-life and the energies and relative intensities of its predominant gamma-rays.
- Comparison of experimental results with data from the 188W[n,gamma]189W reaction and theoretical cross-section ratios.
Main Results:
- The half-life of 189W was determined to be 9.3 ± 0.3 minutes, which differs from the previously reported 10.8 ± 0.2 minutes from the 188W[n,gamma]189W reaction.
- The energies of the two main gamma-rays (260.4 ± 1.3 keV and 421.7 ± 1.4 keV) were consistent between reactions, but their relative intensities showed significant discrepancies.
- An estimated cross-section of 0.5 ± 0.2 mb was suggested for the 192Os[n,alpha]189W reaction, with the absolute intensity of the 260 keV gamma-ray estimated at approximately 50%.
Conclusions:
- The study provides a refined measurement of the 189W half-life and highlights inconsistencies in gamma-ray intensity ratios, suggesting potential differences in production mechanisms or nuclear structure.
- The findings contribute to a better understanding of neutron-induced reactions on osmium isotopes and the decay properties of neutron-rich Tungsten isotopes.
- Further investigations may be warranted to resolve the discrepancies in relative gamma-ray intensities and confirm the estimated reaction cross-section.