Evaluation of the total photoabsorption cross sections for actinides from photofission data and model calculations
Abstract
We have calculated the fission probabilities for 237Np, 233,235,238U, 232Th, and natPb following the absorption of photons with energies from 68 MeV to 3.77 GeV using the RELDIS MonteCarlo code. This code implements the cascadeevaporationfission model of intermediateenergy photonuclear reactions. It includes multiparticle production in photoreactions on intranuclear nucleons, preequilibrium emission, and the statistical decay of excited residual nuclei via competition of evaporation, fission, and multifragmentation processes. The calculations show that in the GeV energy region the fission process is not solely responsible for the entire total photoabsorption cross section, even for the actinides: ~5570% for 232Th, \~7080% for 238U, and ~8095% for 233U, 235U, and 237Np. This is because certain residual nuclei that are created by deep photospallation at GeV photon energies have relatively low fission probabilities. Using the recent experimental data on photofission cross sections for 237Np and 233,235,238U from the Saskatchewan and Jefferson Laboratories and our calculated fission probabilities, we infer the total photoabsorption cross sections for these four nuclei. The resulting cross sections per nucleon agree in shape and in magnitude with each other. However, disagreement in magnitude with totalphotoabsorption crosssection data from previous measurements for nuclei from C to Pb calls into question the concept of a ``Universal Curve'' for the photoabsorption cross section per nucleon for all nuclei.
 Publication:

arXiv eprints
 Pub Date:
 March 2003
 DOI:
 10.48550/arXiv.nuclth/0303070
 arXiv:
 arXiv:nuclth/0303070
 Bibcode:
 2003nucl.th...3070P
 Keywords:

 Nuclear Theory
 EPrint:
 39 pages including 11 figures