ALPHA-DECAY STUDIES OF NEUTRON-DEFICIENT RADIUM ISOTOPES

Neutron-deficient isotopes of radium have been produced in the reactio ns Cl-35 + Lu-175, Ar-40 + Yb-170,Yb-171, and Ar-36 + Yb-170,Yb-171 an d separated in-flight with a gas-filled recoil separator. The activiti es have been identified on the basis of correlated alpha decay chains. The alpha particle energy E(alpha) and the half-life T-1/2 of an isom eric state of the new isotope, Ra-203m, have been determined to be (76 15 +/- 20) keV and (33(-10)(+22)) ms, respectively. An assignment of a nother decay with E(alpha) = (7577 +/- 20) keV and T-1/2 = (1.1(-0.5)( +5.0)) ms to Ra-203g is made on the basis of one observed three-decay chain. Tentative evidence for the production of the new isotope Ra-202 is also given. The values E(alpha) = (7860 +/- 60) keV and T-1/2 = (0 .7(-0.3)(+3.3)) ms were measured. Improved decay data have been obtain ed for Ra-204. The results are E(alpha) = (7484 +/- 10) keV and T-1/2 = (59(-9)(+12)) ms. Earlier findings concerning the decay of two state s in Ra-205 and an isomer in Ra-207 have been confirmed. Approximate v alues for cross sections have been determined for Ra-202, produced usi ng the Ar-36 + Yb-170 reaction and for Ra-203, Ra-204, and Ra-205 usin g the Cl-35 + Lu-175 reaction. The results are 2 nb (Ra-202), 4 nb (Ra -203), 40 nb (Ra-204), and 800 nb (Ra-205).