Volume integrals of the absorptive part of the proton optical potentials

The volume integrals of the absorptive part of proton optical potentials are evaluated for various combinations of the form (surface and/or volume), depth, and geometry of the absorptive potential which have been found to give comparable fits to the data for different targets at a particular energy, and also at different energies. It is concluded that the total (sum of the surface and volume absorptions) volume integral per particle of the absorptive part of the proton optical potential is a well-defined quantity in that it is practically independent of (a) the form (surface and/or volume absorption) and the geometrical parameters employed, (b) the mass number of the target nucleus at each energy, and (c) the incident proton energy in the range 10-60 MeV. Examination of the presently available results yields a value 115 ± 15 MeV ${\mathrm{fm}}^3$ for this quantity. The energy independence of these volume integrals is in contrast with the marked energy dependence observed for the volume integrals of the real part of the optical potentials.