GAMMA-DECAY FROM STATES AT LOW EXCITATION-ENERGY IN THE NEUTRON-DEFICIENT ISOTOPE, RN-200, IDENTIFIED BY CORRELATED RADIOACTIVE DECAY

The low-lying level structure of the neutron-deficient isotope Rn-200 has been studied using the Hf-176(Si-28,4n) reaction at a beam energy of 142 MeV. Evaporation residues were selected using an in-flight reco il mass separator, the Argonne Fragment Mass Analyzer, and implanted i n a double-sided silicon strip detector. Prompt gamma rays in Rn-200 w ere observed at the target position using the AYEBALL array of 19 Comp ton-suppressed germanium detectors, and were identified by the subsequ ent radioactive decay of associated recoiling ions in the strip detect or. Isotopic assignments of the nuclei produced were made on the basis of the mass-to-charge ratio of the recoiling ion and the energy and h alf-life of its alpha decay. Previous results concerning transitions i n Rn-202 were confirmed. The level scheme deduced for Rn-200, compared with those of heavier radon isotopes, is not consistent with the onse t of deformation predicted by theoretical calculations. The estimated production cross section for Rn-200 in this reaction was 5 mu b.