Impact of the electron environment on the lifetime of the 229Thm low-lying isomer

The question of the lifetime of the Th-229(m) low-lying isomer is considered in light of current experimental research. A strong effect of the electron shell on lifetime is demonstrated, depending on the energy of the isomer. Calculations are performed within the framework of the multiconfiguration Dirac-Fock method. The calculated lifetime ranges from around 1 min down to 10(-5) s. Prospects for further experimental research of the isomer are discussed.