Search for 'doorway states' relevant to the production and survival of 180Ta in stars

Full text: The process by which 180Ta is produced in stars is not clear. The problem is especially interesting because 180Ta occurs in nature as an isomeric state with T7/2>1.2x1015yr, even though its ground state has a much shorter lifetime (T1/2=8.1hr) and photo-induced depopulation of the quasi-stable isomer is possible under conditions that could be expected in a start. Some of the observed resonances that enable depopulation of the isomer have been associated with known states in a Kπt=5- rotational band and specific predictions of the y-ray decay branches towards the ground state and the isomeric state have been made. We have used the 180Hf(d,2n) reaction to populate the Kπ=5- band with higher intensity than previous measurements. The results of our search for the predicted y-ray decays will be presented. Copyright (2005) Australian Institute of Physics