High resolution resonant Auger spectra have been measured at the VUV beam line at ELETTRA, Sincrotrone Trieste, while tuning the photon energy across the ${2p}_{3/2}^{-1\mathrm{}}3d$ resonance of argon. A large variation of the branching ratio for decay into the spectator ${3p}^{-2\mathrm{}}3d$ and shakeup ${3p}^{-2\mathrm{}}4d$ channels is observed. The effect has not been seen previously in resonant inner-shell excitation and is attributed to the interference between the direct photoionization process and resonant Auger decay leading to the same final state.

• Received 22 March 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.2646