Isotopic Production Cross Sections Research Articles

Microscopic and Macroscopic Model Calculations of Relativistic Heavy-Ion Fragmentation Reactions

The possibility of observing previously postulated neutron-proton correlations in the nuclear ground state via relativistic heavy-ion reactions is examined. The isotope-production cross sections from the reaction of 213-MeV/nucleon $^{40}\mathrm{Ar}$ with $^{12}\mathrm{C}$ are calculated with a correlated abrasion-ablation model and with an uncorrelated intranuclear cascade model, and the results compared to recent experimental data. The neutron-proton correlations may only be visible in products near the mass of the fragmenting nucleus.

Some regularities in the production of isotopes with 4 ≦ Z ≦ 9 in the interaction of 22Ne with 232Th

In the bombardment of 232Th with 22Ne ions with an energy of 172 MeV the energy spectra and production cross sectionslfor isotopes of elements ranging ifrom Be to F have been measured at an emission angle of 12°. It is shown that all of the isotopes detected have been produced by deep inelastic collisions of the initial nuclei, i.e. the kinetic energies of the reaction products are close to the exit Coulomb barriers. It is found that the energy spectra widths (FWHM), relative yields at 12° and 40° and the Q gg dependences of isotopic production cross sections differ considerably for stable, neutron-deficient and neutron-rich isotopes. This difference can be interpreted as being due to a contribution from secondary processes such as α-particle and nucléon evaporation from the excited 22Ne and light transfer reaction products. The data obtained can be employed to choose optimal conditions for the detection of the extremely neutron-rich isotopes of light elements produced in multinucleon transfer reactions.

Independent yields of Rb and Cs isotopes from the fission of natural uranium induced by protons of energy 80 and 100 MeV

The independent yields or production cross sections of rubidium isotopes from mass 86 to 97, and of cesium isotopes from mass 129 to 144, have been measured for the fission of natural uranium induced by 80 and 100 MeV protons. The results were obtained by means of an on-line mass spectrometer. The rubidium distributions are quite symmetric, whereas the cesium distributions show a definite skewness toward the heavy mass side. Comparison with other results at 40, 50, 60 and 150 MeV proton energies shows that the heavy mass sides of the isotopic distributions are relatively insensitive to proton energy, whereas the light mass sides shift downward with increasing proton energy. The average total number of neutrons emitted has been estimated for each fission reaction. The mechanism of nuclear charge division in 80 and 100 MeV proton fission in the mass split studied here appears to be similar to that operating in thermal-neutron and low-energy proton fission.

Production cross sections of lithium and beryllium isotopes in 12C by high-energy protons and alpha particles

Abstract The formation cross sections of 6Li, 7Li and 7Be, 9Be, 10Be by high-energy protons and α-particles in a 12C target have been determined by a high sensitivity mass-spectrometric technique. A method for extracting lithium and beryllium from the irradiated graphite without interference by natural contamination has been developed. Cross sections have been measured for 150 MeV and 600 MeV protons as well as 100–140 MeV α-particles. The 9Be and 10Be cross sections from 12C are significantly higher than the corresponding ones on 16O measured previously. The implications of the high values of α-induced cross sections on the study of cosmic-ray propagation are briefly discussed.

Mass Spectrometric Studies of the Interaction of Gold with 3.0-Bev Protons

Gold targets have been irradiated with 3.0-Bev protons and the yields of cesium, barium, and rubidium nuclides investigated by mass spectrometry. A high-sensitivity surface-ionization technique, using a multiple filament source arrangement and capable of determining (within 5%) ${10}^{8}$ alkali metal atoms, was developed. The separation of products from the gold target was accomplished by extracting the gold into diethyl ether. The contamination level of stable ${\mathrm{Cs}}^{133}$ in the gold foil and reagents was determined by isotope dilution methods to be \ensuremath{\sim}9\ifmmode\times\else\texttimes\fi{}${10}^{9}$ atoms. Ratios of production cross sections for neutron-deficient cesium isotopes and their barium parents were calculated from mass spectra. Cross sections were placed on an absolute scale by a radiochemical determination of the ${\mathrm{Cs}}^{127}$ cross section. No cesium isotopes with $A>128$ are formed in appreciable independent yield. An upper limit of 0.002 mb was placed on cross sections for ${\mathrm{Cs}}^{132}$ and the neutron-excess cesium isotopes. No stable cesium resulting from nuclear reactions was detected above the natural contamination background. Ratios of production cross sections for rubidium radioisotopes were determined. The natural contamination of rubidium was too large to place a meaningful limit on stable rubidium production.