Self-energy of image states on copper surfaces

We report extensive calculations of the imaginary part of the electron self -energy in the vicinity of the (100) and (111) surfaces of Cu. The quasipar ticle self-energy is computed by going beyond a fret-electron description o f the metal surface, either within the GW approximation of many-body theory or with inclusion, within the GW Gamma approximation, of short-range excha nge-correlation effects. Calculations of the decay rate of the first three image states on Cu(100) and the first image state on Cu(111) are also repor ted, and the impact of both band structure and many-body effects on the ele ctron relaxation process is discussed. [S0163-1829(99)03940-5].