Controlling core-hole lifetime through an x-ray planar cavity

It has long been believed that the core-hole lifetime (CHL) of an atom is an intrinsic physical property, and controlling it is significant yet is very hard. Here, the CHL of the $2p$ state of a W atom is manipulated experimentally by adjusting the emission rate of a resonant fluorescence channel with the assistance of an x-ray thin-film planar cavity. The enhanced emission rate is linearly accelerated by the photonic density of states inside the cavity, which can be directly controlled by adjusting the cavity field amplitude through choosing different cavity modes or changing the angle offset in experiment. This experimental observation is in good agreement with the prediction of a developed theoretical model. It is found that the manipulated resonant fluorescence channel can even dominate the CHL. The controllable CHL realized here will facilitate the nonlinear investigations and modern x-ray scattering techniques in the hard x-ray region.