Some recent developments in the 181Ta(6.2 keV) ‐spectroscopy

The 6.2 keV level of 181Ta(T1/2=6.8 μs) belongs to the few Mossbauer resonances with lifetimes in the microsecond region. The corresponding natural linewidth, Wo=6.5 μm/s, has not been observed so far. In spite of many efforts, the best experimental linewidths are still a factor of ∠10 larger than Wo1,2. In this contribution we report a new method of source preparation from cyclotron‐produced, carrier‐free 181W activity, which yields either an improvement in the experimental linewidth or in the source efficiency. The hitherto method of source production from neutron activated 181W(180W(n,γ)181W) suffered from a relatively low specific activity, where even with high‐flux neutron irradiations only ∠100 mCi/mg could be obtained3. In contrast, a 181W production by a deuteron (or proton) bombardment of a Ta foil (181Ta(d,2n)181W) followed by a chemical separation of the carrier material (by ion exchange chromatography) can provide specific activities up to ∠4000 mCi/mg. From 15 mCi of carrier‐free 181W activit...