MEASUREMENT OF COMPOUND NUCLEUS SPACE-TIME EXTENT WITH 2-NEUTRON CORRELATION-FUNCTIONS

Two-neutron relative-momentum correlation functions have been measured in the 130 MeV O-18 + Mg-26 reaction. Differences in the longitudinal and transverse correlation functions, observed for the first time for neutrons, allow an independent determination of the spatial extent an d the time scale for decay of the Ca-44 compound nucleus. A comparison with theoretical calculations indicates a radius of 4.4 +/- 0.3 fm an d an average neutron emission time scale of 1100 +/- 100 fm/c for Ca-4 4 at 100 MeV excitation energy. Correlation functions selected by cuts on the total momentum of the neutron pair give a quantitative charact erization of the cooling of a compound nucleus.