High-resolution threshold photoelectron study of the Kr 4s satellite states

Abstract High-resolution threshold photoelectron spectra of Kr were measured in the photon energy region between the Kr + 4s −1 main line and the Kr 2+ 1 D 2 state. The measured peak width was close to 7 meV. Rich satellite structures, 178 peaks including 48 newly observed peaks, were found in these spectra. Assignments of these levels were performed by comparison with previous optical, photoelectron, and threshold photoelectron measurements. The Rydberg series converging to the Kr 2+ 3 P 2 states, which had not been observed, as well as three Rydberg series converging to the Kr 2+ 1 D 2 states, some levels of which had been observed, were observed. The energy levels of the Kr 2+ 3 P 2 and 1 D 2 states as converging limits of the observed Rydberg series were obtained as 38.355 and 40.180 eV, respectively.