Franz Käppeler and evolutions in nuclear physics

This is a paper on the remarkable evolution in the career of Franz Käppeler that started with the measurements of neutron cross sections of various materials, followed by studies of key nuclei for the slow neutron capture process (s-process) in search of the origins of half of the heavy elements, and eventually to the measurements of the lifetimes of long-lived isomers identified in nuclei along the branching points of the s-process. This evolution of scientific interest took place over 4–5 decades and included the development of new tools and techniques that were implemented into the construction of new facilities for nuclear physics coupled with advances in both astronomical observations and theoretical approaches in modeling. Franz Käppeler led an exemplary life in his love of Rosel, good friends, great champagne, and those ever-elusive neutrons and their interactions with nuclei resulting in the various wonders of the universe.