Electric-dipole-forbidden nuclear transitions driven by super-intense laser fields

Electric-dipole-forbidden transitions of nuclei interacting with super-intense laser fields are investigated by considering stable isotopes with suitable low-lying first excited states. Different classes of transitions are identified, and all magnetic sublevels corresponding to the near-resonantly driven nuclear transition are included in the description of the nuclear quantum system. We find that large transition matrix elements and convenient resonance energies qualify nuclear $M1$ transitions as good candidates for the coherent driving of nuclei. We discuss the implications of resonant interaction of intense laser fields with nuclei beyond the dipole approximation for the controlled preparation of excited nuclear states and important aspects of possible experiments aimed at observing these effects.

Figure 1

Number of signal photons per nucleus per laser pulse, $N_{\mathrm{SIGNAL}}$, for several isotopes with first excited states below 12.4 keV (green squares) and above 12.4 keV (red crosses). The results are plotted versus the atomic number $Z$. The European XFEL considered has a pulse duration of 100 fs and an average brilliance of $1.6\times {10}^{25}$ photons/(s mrad${}^2$ mm${}^2$ 0.1%bandwidth).

Figure 2

Signal photons per second for laser driving of nuclear transitions with energies (A) below 12.4 keV and (B) above 12.4 keV. The energy of the nuclear transition is given on the abscissa. The green squares denote $E1$ transitions, the blue circles $E2$ transitions, and the red crosses $M1$ transitions. The considered experimental laser and target parameters are discussed in Sec. 3b.