30 YEARS OF MGR - HOW IT CAME ABOUT, AND WHAT CAME OF IT

Starting from some personal recollections about the origins of the MGR model of electronically stimulated desorption, in particular on the M G side, I give a subjective view of the developments it initiated, the generalizations it allows, and the spin-offs it produced. The basic c oncept of the competition between the evolution of a repulsive excitat ion along its dissociation coordinate(s) and the quenching of that exc itation by energy and/or charge exchange is stressed, which can also b e characterized as interplay of localization and delocalization of the excitation. Some examples for recent extensions of the model which ca n explain novel, more detailed observations will be given. These inclu de very recent observations in this laboratory of extremely high vibra tional excitations in ESD-produced CO from group VIII metal surfaces, which can be readily understood on the basis of the MGR mode! applied to the internal (molecular) and external (adsorbate-substrate) coordin ates in these systems.