Ionization potential depression (IPD) is a phenomenon where the threshold energy required to ionize an ion in dense plasmas——by exciting one of its bound electrons to the continuum——in lower than that of an equivalent isolated ion. The IPD effect can significantly affect plasma properties, including opacity and equation of state, and is therefore highly important for astrophysics, planetary science, and inertial confinement fusion (ICF) research. However, current knowledge of IPD in diverse scenarios is limited, and investigating IPD through experimental measurements or theoretical simulation is challenging, as theoretical results often differ from one another. In this report, we present observations of IPD in warm dense carbon systems using X-ray Thomson scattering. By measuring plasma conditions in carbon plasmas of varying densities, we verify IPD models and determine the effects of environmental density on plasma ionization states. Ths work will improve understanding of atomic structure in plasmas under extreme condictions and promote the development of plasma physics in astrophysics, planetary science, and inertial confinement fusion research.
 

ionization potential depressions,Warm Dense Matter,X-ray Thomson scattering.