The carbon Auger line shapes obtained from three diverse gas-phase transition-metal carbonyls are analyzed. Some features in the line shape directly reflect the amount of $\pi$ backbonding. The analysis indicates that the dominant initial state is the adiabatically relaxed ground state. The final-state holes are either localized on the same ligand or described by a state consisting of one hole on a ligand and the other on the metal atom. The latter state may be viewed as a $\pi$-backbonding—assisted interatomic decay.

• Received 12 August 1980

DOI:https://doi.org/10.1103/PhysRevLett.46.911