KONDO SCATTERING OBSERVED AT A SINGLE MAGNETIC IMPURITY

Electron scattering of isolated Ce adatoms on Ag(111) surfaces was stu died with a low-temperature scanning tunneling microscope. Tunneling s pectra obtained on and near Ce reveal a characteristic dip around the Fermi energy which is absent for nonmagnetic Ag adatoms. This feature is detected over a few atomic diameters around Ce atoms at the surface . The transition matrix element from the localized f electron to the t unnel-current carrying continuum states bears a strong resemblance to discrete autoionized states. We interpret the dip spectrum as a Fano i nterference for the limit where the f orbital has a very small matrix element.