An IGISOL portrait

Abstract

This issue of Hyperfine Interactions consists of 21 articles describing scientific work related to the research at the on-line isotope separator facility IGISOL at the University of Jyvaskyla, Finland. Ten contributions containing a significant amount of original results, earlier unpublished, have been presented as a Topical Collection in the European Physical Journal (EPJA 48 issue No 4, 2012). In the early 1980s, the Ion Guide Isotope Separator On-Line (IGISOL) concept was realized at the 20 MeV proton cyclotron of the Physics Department at the University of Jyvaskyla (JYFL). For the first time, the technique allowed the production of high quality ISOL beams from nuclear reaction products with millisecond delay times without chemical restrictions. By providing access to short-lived isotopes of refractory elements it opened up new regions in the nuclear chart for nuclear decayand ground-state spectroscopy. During the 1980s, the main research activity at IGISOL was decay spectroscopy, and in particular, of fission products produced in proton-induced fission of natural uranium. Approximately 40 new isotopes and isomers were discovered and studied employing beta-, gamma-, and conversion electron spectroscopy. These experiments covered a broad range of neutron-rich nuclei from yttrium (Z = 39) to cadmium (Z = 48) and revealed how their structure was developing between highly deformed zirconium through triaxial ruthenium isotopes to weakly deformed vibrational cadmium isotopes. The original IGISOL facility was shut down in October 1991 and was reinstalled as IGISOL-2 at the science campus housing the laboratory for the K = 130 MeV heavy ion cyclotron. A new window of opportunity for extending research to neutrondeficient nuclei far from stability was opened and was going to have a strong impact