X ray absorption spectrum of O2

The x ray absorption spectrum of the O 2 molecular cation is measured. The ions are stored in a cryogenically cooled radiofrequency ion trap and probed by tunable synchrotron radiation. The spectrum exhibits several salient features a three state composite amp; 120587; resonance at the low energy side followed by a two component exchange split, a highly dissociative, amp; 120590; resonance pulled down well below the ionization limit; and a complex valence Rydberg high energy part, including several resolved bands. Small structures are interpreted as correlation state satellites with leading internal or semi internal configurations. Calculations using the restricted active space wave functions and quantum wave packet dynamics offer an overall excellent interpretation of the spectral features