Natural line widths are measurable fundamental quantities of quantum states that, in atoms and molecules, characterize the lifetime of the electronic states and therefore carry information about electronic structure and transition matrix elements. For core-levels, their determination is based on various types of spectroscopic measurements such as the photoabsorption or the photoelectron spectroscopy for core-excited and core-ionized states, respectively. The values reported in the literature used to change over the years owing to the improvement of the experimental accuracy available at synchrotron storage rings. We report here, in a broad energy range, the natural line widths for a series of core-levels in atoms (Kr3d, Ar2p, Xe3d) and molecules (S2p in CH 3 SSCH 3 , B1s in BF 3 , Cl2p in HCl, C1s in CO, C 2 H 2 , CH 4 and CF 4 , N1s in N 2 , O1s in O 2 , CO and CO 2 ), based on ultrahigh resolution total ion yield or X-ray photoelectron spectroscopy (XPS) measurements at the PLEIADES beamline at SOLEIL synchrotron (France). These newest measurements of the lifetime broadening of core levels are compared with previously published experimental results.
