Element 107

Abstract

We identified two α-emitting isotopes of element 107 with masses of 261 and 262 respectively by parent-daughter correlations. For the isotope with mass 262 we found two transitions with (102±26) ms and (8.0±2.1) ms half-life, which we assign to the groundstate and to an isomeric transition, respectively. The half-life of the isotope with mass 261 is (11.8-2.8+5.3) ms. Spontaneous fission, which could be assigned to the decay of an isotope of element 107, was not detected in our experiments. This observation is in-line with our previous results, indicating a region of nuclei with strong microscopic stabilisation in the trans-actinides. Both new isotopes were produced by complete fusion of209Bi with54Cr. The production cross sections are (163±34) pb for262107 and (36-14+22) pb for261107. © 1989 Springer-Verlag.