  Resonance fluorescence of laser-driven highly charged ions is studied in the
relativistic regime by solving the time-dependent master equation in a
multi-level model. Our ab initio approach based on the Dirac equation allows
for investigating highly relativistic ions, and, consequently, provides a
sensitive means to test correlated relativistic dynamics, bound-state quantum
electrodynamic phenomena and nuclear effects by applying coherent light with
x-ray frequencies. Atomic dipole or multipole moments may be determined to
unprecedented accuracy by measuring the interference-narrowed fluorescence
spectrum.
