Nuclear Reactions of Tantalum with 5.7-Gev Protons

Abstract

Radiochemically determined cross sections are reported for sixty-seven of the nuclides which appear as products of the nuclear reactions between 5.7-Gev protons and tantalum, and upper or lower limits are reported for thirty additional product nuclides. These data are distributed throughout the range of mass numbers $7<A<\mathrm{}180\mathrm{}$. The mass yield distribution obtained from the data is similar to the distribution reported by Wolfgang et al. for the interactions of 3-Gev protons with lead, and is consistent with their observations that (1) all mass numbers less than that of the target are represented with cross sections of at least a few millibarns; and (2) there is no obvious fission peak, even though a fission peak is clearly seen at lower bombarding energies (0.3 to 0.5 Gev). However, an objective criterion is devised which, when applied to the data, gives a result supporting the view that at least one reaction process other than spallation (presumably fission) is necessary to explain the observed shape of the mass yield distribution. Although for product mass numbers above $A\approx 70$ most of the measured cross sections represent "chain yields" of neutron-deficient nuclides, it is possible to determine the approximate locus in the $N$, $Z$ plane of the line of isobaric independent yield maxima, up to $A\approx 150$. This line is compared with various calculated lines, given in the high-energy nuclear evaporation paper by Dostrovsky, Rabinowitz, and Bivins, in an effort to extract new information on the average excitation energy and neutron deficiency (or excess) of the nuclear evaporation progenitors as functions of the mass number, and on the nuclear state density parameter $a$.