Two-neutron radioactivity and four-nucleon emission from exotic nuclei.

A theoretical method for estimates of a width of "true" four-nucleon decays is developed. Several candidate isotopes to possess this property are considered. Our lifetime estimates compare one-neutron, true two-neutron, and true four-neutron emissions at similar conditions. Prospects of experimental search for two-neutron, four-proton, and four-neutron radioactivity are discussed. [ABSTRACT FROM AUTHOR]