Alpha-particle emission probabilities in the decay of U-238

U-238 decays by alpha-particle emission to Th-234. No direct measurements o f alpha-particle emission probabilities (P-alpha) of this nuclide have been reported since 1961, and recommended values for P-alpha have remained unch anged for years, until recent evaluations suggested new values. This work p resents the results of new measurements made with Si detectors and sources of natural uranium. The results obtained for the analysis of twenty spectra are: P-alpha 0 = 0.7754 +/- 0.0050, P-alpha 50 = 0.2233+/-0.0050 and P-alp ha 163 = 0.0013 +/- 0.0003. (C) 2000 Elsevier Science Ltd. All rights reser ved.