Isolated core excitation of autoionizing Rydberg states

A novel spectroscopic technique, Isolated Core Excitation (ICE), is described and used to measure the energies, linewidths and wavefunctions of some highly excited autoionizing states of barium atoms. In these experiments, three lasers are used to excite an effusive beam of barum atoms. Two lasers are used to isolate the bore of the atoms, by exciting one of the valence electrons to a Rydberg state with a large principal quantum number. The third laser is used to excite the core (i.e., the other valence electron). A detailed model of these core transitions is presented using simple hydrogenic wavefunctions and Multichannel Quantum Defect Theory (MQDT). Three series of measurements were performed to verify the validity of various aspects of the theoretical model, including multiconfiguration effects and laser power effects. Agreement between the model and the experimental data is found to be excellent