Oscillatory electron-phonon coupling in ultra-thin silver films on V(100)

The temperature dependence of peak widths in high-resolution angle-resolved photoelectron spectroscopy from quantum well states in ultra-thin Ag films on V(100) has been used to determine the electron-phonon coupling constant , lambda, for films of thickness 1-8 layers. A strong oscillatory variation in coupling strength is observed as a function of film thickness, peaking at a two layer film for which lambda similar or equal to 1.0. A simple theo ry incorporating interaction of the photo-hole with the thermal vibrations of the potential step at the adlayer-vacuum interface is shown to reproduce the main features of these results.