Tuned Electron-nucleus Resonance as a Tool of Producing the 229mTh isomer

Possible ways of resonant optical pumping of the 8.36-eV 229mTh nuclear isomer – the most likely candidate for the role of a nuclear frequency standard – are discussed. The two-photon laser-assisted mechanism is generalized to optical pumping of the isomer through the electronic bridge transition in externally applied field of three radiative sources. Attention is focused on the role of the final atomic state width. Its proper variation allows one to make use of the resonating properties of the electron shell to have a gain in the pumping rate of orders of magnitude.