Nuclear excitation by laser-assisted electronic transitions

The excitation of nuclear states by electric and magnetic multipole transitions of bound electrons in the presence of a strong laser field is studied. The excitation probability is calculated for general time-dependent electronic states in first-order perturbation theory. An adiabatic description of the dressed electron states in the laser field allows an easy calculation of the excitation function. Ionization effects caused by the laser are considered in a simple manner. The probability for the excitation of the nuclei $_{66}^{161}\mathrm{Dy}$, $_{76}^{189}\mathrm{Os}$, $_{77}^{193}\mathrm{Ir}$, $_{79}^{197}\mathrm{Au}$, $_{92}^{235}\mathrm{U}$, and $_{93}^{237}\mathrm{Np}$ is investigated as a function of the laser intensity and the photon energy. The increase of the excitation probability is limited by the ionization of the atom and the lifetime of the states. The de-excitation of the 3/${2}^{+}$ (3.5\ifmmode\pm\else\textpm\fi{}1.0 eV) state in $_{90}^{229}\mathrm{Th}$ is an example of the laser-assisted discrete internal conversion. \textcopyright{} 1996 The American Physical Society.