Isotope effects in the harmonic response from hydrogenlike muonic atoms in strong laser fields

Abstract

High-order harmonic generation from hydrogenlike muonic atoms exposed to ultraintense high-frequency laser fields is studied. Systems of low nuclear-charge number $Z$ are considered where a nonrelativistic description applies. By comparing the radiative response for different isotopes, we demonstrate characteristic signatures of the finite nuclear mass and size in the harmonic spectra. In particular, for $Z>1$, an effective muon charge appears in the Schr\"odinger equation for the relative particle motion, which influences the position of the harmonic cutoff. Cutoff energies in the million-electron-volt domain can be achieved, offering prospects for the generation of ultrashort coherent $\ensuremath{\gamma}$-ray pulses.