Modification of nuclear transitions in stellar plasma by electronic processes: K-isomers in 176Lu and 180Ta under s-process conditions

摘要

The influence of the stellar plasma on the production and destruction ofK-isomers is studied for the examples 176Lu and 180Ta. Individualelectromagnetic transitions are enhanced predominantly by nuclear excitation byelectron capture, whereas the other mechanisms of electron scattering andnuclear excitation by electron transition give only minor contributions. It isfound that individual transitions can be enhanced significantly for lowtransition energies below 100 keV. Transitions with higher energies above 200keV are practically not affected. Although one low-energy transition in 180Tais enhanced by up to a factor of 10, the stellar transition rates from low-K tohigh-K states via so-called intermediate states in 176Lu and 180Ta do notchange significantly under s-process conditions. The s-process nucleosynthesisof 176Lu and 180Ta remains essentially unchanged.