Introductory Lecture - Excited states at surfaces: Fano profiles in STM spectroscopy of adsorbates

The Fano-Anderson model for a discrete state embedded within a continuum is revisited within the context of excitation and decay processes which lead to some manifestations of Fano lineshape profiles. The phenomenon of resona nce tunneling between an STM tip and a metal surface upon which there are i solated adsorbed atoms is discussed and the relationship between the spectr oscopic signature of such systems and that of the Fano profile is taken up. Recent experimental studies of Kondo systems of magnetic adsorbates such a s Co and Ce adsorbed on noble metal (111) surfaces have motivated this work .