No abstract

The cross sections for double photoionization of helium and the ratios of double to single ionization have been measured from the double-ionization threshold to 820 eV. The results are in very good agreement with several recent calculations. ͓S1050-2947͑98͒05403-1͔ PACS number͑s͒: 32.80.Fb

Relative photoionization cross sections for O + and O 2+ produced by the Auger decay of a 1s hole in atomic oxygen were measured by using synchrotron radiation between 525 and 553 eV. Energies and quantum defects of the members of the two Rydberg series converging to [1s]2s 2 2p 4 ( 4 P) and [1s]2s 2 2p 4 ( 2 P) ionization thresholds were determined. In addition, the 2 P and 4 P ionization thresholds were calculated from the two Rydberg series. The 182 meV resolution of the monochromator allowed a detailed study over both thresholds revealing evidence for post-collision interaction and allowing a comparison of the ionization continuum above both 2 P and 4 P thresholds with that of the ionization continuum above the Ar L 2-3 edges. This comparison indicates that the lifetimes of the Ar(2p) and O(1s) hole states are approximately the same.

The presence and role of polysulfide radicals in the electrochemical processes of lithium sulfur (Li–S) batteries is currently being debated. Here, first‐principles interpretations of measured X‐ray absorption spectra (XAS) of Li–S cells are leveraged with an ether‐based electrolyte. Unambiguous evidence is found for significant quantities of polysulfide radical species (LiS3, LiS4, and LiS5), including the trisulfur radical anion S3 −, present after initial discharge to the first discharge plateau, as evidenced by a low energy shoulder in the S K‐edge XAS below 2469 eV. This feature is not present in the XAS of cells at increased depth of discharge, which, by our analysis, exhibit increasing concentrations of progressively shorter polysulfide dianions. Through a combination of first‐principles molecular dynamics and associated interpretation of in situ XAS of Li–S cells, atomic level insights into the chemistries are provided that underlie the operation and stability of these batteries.

Degradation mechanism of rechargeable lithium/sulfur-graphene oxide cell was studied using scanning electron microscopy and X-ray spectroscopy.