Decay of isomers stimulated by laser radiation

A theory is presented for the induced decay of isomer levels for nuclei exposed to a laser field, which couples the initial isomer level to intermediate higher lying levels with short lifetimes. We took into account the electric dipole transitions between these levels in a one-photon approximation. The time-dependent Schroedinger equation with a periodic Hamiltonian is solved by the method of the composite Hilbert space. A simple expression for the broadening of the isomer level Delta Gamma, caused by the laser radiation, is derived. As an example, we considered the decay of the isomer level 970.17 keV with the spin Ipi = 23/2- of 177Lu, coupled by the laser wave to the virtual level 1352.33 keV with Ipi = 21/2+. The ratio of the broadening ΔΓ to the natural width of the isomer level Γ is found to be about 40% for a 1017 W/cm2 laser. Any influence of the electronic environment is not taken into account. (authors)