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