Production of the New Isotope ²⁵⁵Db

It is challenging to produce neutron-deficient nuclei of super heavy elements due to low production cross sections. There have been previous claims of the observation of the light-dubnium isotope ²⁵⁵Db [1-3], however none of these have been confirmed or accepted by the community as an identification. An experiment was performed at the Lawrence Berkeley National Laboratory’s 88-inch cyclotron facility in an attempt to produce both the previously observed isotope ²⁵⁶Db and the new isotope ²⁵⁵Db. The fusion evaporation reaction ²⁰⁶Pb(⁵¹V, 1-2n)^255-256Db was chosen for the production of these dubnium isotopes, which took place upstream of the Berkeley Gas-filled Separator (BGS). The BGS then served to separate the dubnium isotopes from any unreacted beam material of reaction by-products. The decay properties of the dubnium isotopes could then be observed with a double-sided silicon-strip detector that was installed at the BGS focal plane. Preliminary results from this measurement will be presented.

1. G.N. Flerov, JINR-E7-10128, (1976).

2. A.-P. Lepp ̈anen, PhD Thesis, University of Jyv ̈askyl ̈a (Finland) Research Report No. 5/2005 (2005).

3. F. P. Heßberger, Eur. Phys. J. A (2017) 53: 75.