Triggering of nuclear isomers via decay of autoionization states in electron shells (NEET)

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Nuclear excitation by an electron transition (NEET) may be used for triggering the decay of nuclear isomers only when there are compensations between energies (ΔE) and multipolarities (ΔL) of the nuclear transition and the transition in an electron shell. It is shown that using the autoionization states (AS) allows one to compensate for the ΔE and ΔL differences. Laser radiation may be used for the excitation of AS with energies up to 10–15 eV and 229m Th (3.5 eV) nuclear isomer excitation by NEET via AS decay. Ion beams, electron beams, and X rays may be used for the excitation of the trigger nuclear levels with energies up to 150 keV by NEET via AS and for the triggering of the nuclear isomer decay. For excitation of AS with the energies up to 150 keV, two or more hole states in deep inner electron shells must be excited. The cross section for such two-hole state excitation in electron shells by ion beams may be sufficiently high. The possibilities of NEET via AS for the triggering of nuclear isomer decay are discussed.