We have measured participator and spectator decay at several photon energies within the range of the lifetime-broadened first vibrational component of the C $1s\to {\pi }^{*}$ resonance in CO. From the branching ratios it is evident that the resonant enhancement is different for single-hole and two-hole–one-electron states: The maximum in the resonant intensity peaks at different photon energies. It now becomes necessary to calculate energy-dependent transition matrix elements within the lifetime-broadening range.

• Received 19 August 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.4302