Lifetime measurements by delayed coincidences with and without a complete knowledge of the prompt curve. Application to levels in 184Ir and 185,187Pt

A method is described which enables one to deduce a range of possible values for the lifetime of a nuclear level when the delayed coincidence curve is experimentally given and the prompt curve is known only through some of its features. The method still applies when a prompt contribution is present. Experimental data in 184Ir are analyzed, and yield T1/2(293 keV) = 1.1(3) ns, T1/2(70.7)<180ps. The method is also used to discuss results obtained with an experimental prompt curve in 185Pt [T1/2(201) = 728(20) ps] and 187Pt[T1/2(260) = 163(6) ps, T1/2(181) = 1.68(4) ns].