Plasmon loss structure in synchrotron radiation photoemission from Mg films

Synchrotron radiation excitation has been used to vary the kinetic energy of electrons photoemitted from the 2p core level of polycrystalline magnesium films and the energy-dependence of the accompanying plasmon loss structure has been observed. Difficulties associated with background subtraction are discussed, and it is shown that the method of background subtraction profoundly affects the conclusions drawn from such an experiment on the relative importance of plasmon and single particle excitation mechanisms for electron scattering. Very thin films of Mg have also been studied in an attempt to separate the intrinsic and extrinsic modes of plasmon creation. Although the plasmon loss structure is dependent on film thickness implying a considerable contribution from extrinsic processes, we are not able to observe plasmons excited in the thin film by electrons originating in the substrate core level. The implications of these results are discussed and further experiments suggested.