Photoassociation spectroscopy in Penning ionization reactions at   sub-Kelvin temperatures
  Penning ionization reactions in merged beams with precisely controlled collision energies have been shown to accurately probe quantum mechanical effects in reactive collisions. A complete microscopic understanding of the reaction is, however, faced with two major challenges---the highly excited character of the reaction's entrance channel and the limited precision of even the best state-of-the-art ab initio potential energy surfaces. Here, we suggest photoassociation spectroscopy as a tool to identify the character of orbiting resonances in the entrance channel and probe the ionization width as a function of inter-particle separation. We introduce the basic concept and discuss the general conditions under which this type of spectroscopy will be successful. 
Wojciech Skomorowski, Yuval Shagam, Edvardas Narevicius, Christiane P.   Koch
physics.atom-ph quant-ph