Analysis Using Ion Induced g Rays

Abstract

Gamma ray energies and some thick sample reaction yields are summarized for proton, deuteron, triton, 3He and IX-particle induced )' rays which have been used in prompt nuclear analysis work.The tabulation of ion induced y-ray energies and intensities, for use in prompt nuclear analysis, would be straightforward if only one or a few ions and ion energies were in use, as is the case for neutron induced y rays. This is not the case and the tabulation of useful information must involve a compromise between completeness and unwieldiness. For example, the table of y-ray energies presented by de Meijer et al. (1973) includes all possible transitions in light elements as derived from the known energy levels of light nuclei. The table is so complex that it is of little use in analysis work, particularly that involving thick samples for which only the strongest y rays are likely to be observed, and individual resonances are of little importance.There have been many reports listing prompt y rays which are useful in analytical applications and from these a compilation has been prepared in order of y-ray energy. Table 1 includes y rays from reactions with the following incident ions: 1 H, 2D, 3H, 3He and 4He. For proton induced y rays, the table does not include all high energy y rays from individual resonances since these are seldom used for analysis even though lists have been presented in the literature.Measurements have been made, using the AAEC 3 MeV Van de Graaff accelerator, of the thick sample yield of y rays from a number of elements. A Ge(Li) detector was used at a distance of 15·5 cm from the sample surface and at 135 0 relative to the direction of the incident ion beam. Elemental samples were mounted on a computercontrolled sample changer so that measurements could be sequenced to give a comparison of yields from various elements. Pulse height spectra in 8192 channels were stabilized using source y rays at 0·511 and 1·274 MeV. A 0·6 mm thick aluminium window was used between the sample and detector in order to minimize y-ray attenuation. The detector efficiency was 19 % at 1· 333 MeV, relative to a 7· 5 by 7·5 cm NaI detector.Spectral analysis to obtain peak areas was carried out using a peak search routine which has been checked in international comparisons of spectrum analysis techniques. Corrections for detector efficiency and solid angle have been made to obtain the yield values given in Table 2. The values for sodium were confirmed by comparison with yields observed from a crystal of NaCI and from a glass sample of known composition.