A computer program is described to perform the identification of isotopes in neutron activated samples. The γ-ray energies
as obtained from a Ge(Li) γ-ray spectrum are compared with those of a library, containing data for about 250 isotopes. Isotopes
whose γ-ray energies match closely with the unknowns are selected as possible constituents. Unlikely attributions are then
eliminated by a careful inspection of the γ-rays found. Further exploitation of half-life, the way of production and the sensitivity
for the given irradiation and measurement conditions, allow the selection of the most likely constituents in the source. The
results of the automated identification agree closely to those obtained by an experienced investigator. The program is written
in FORTRAN IV for a PDP-9 computer with a 16 K word memory.
A tabulation of about 2000 precise gamma-ray energies of about 250 isotopes formed through neutron activation has been used
for the computer-assisted identification of the individual gamma emitters in complex gamma spectra. The identification consists
in the calculation of the gamma-ray energies from the peak maximum position by taking into account the deviation from linearity
of the spectrometer. Successive comparison of these energies with the energies of the tabulation allows then identification.
The identification procedure was tested on a number of samples of varying complexity and satisfactory results were obtained.
The gamma ray energies of nearly all radionuclides formed by reactor neutron irradiation have been determined using high resolution
Ge(Li) spectrometry. The re-producibility of the determinations is demonstrated and, to estimate the accuracy of the measurements,
the results are compared with those of other investigators. In the energy range from 80 to about 1400 keV the accuracy for
the most abundant gamma rays is better than 0.2 keV. The energies of gamma transitions above 1400 KeV may be less accurate.
The data are compiled in an atomic number and in a photon energy sequence. A table of characteristic X-rays is also included.
The tables are intended to be helpful in the identification of isotopes in neutron activation analysis.
Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions
on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:122Sn(n,γ)123mSn:σth=0.145 barn, I=0.79 barn;122Sn(n,γ)113Sn:σth=0.52, I=25.4 barn;112Sn(n, 2n)111Sn:
Two methods are described to determine indium and managenese in high-purity tin. In the first method indium and manganese
are separated from the tin and antimony matrix activities on Dowex 1X8 anion exchanger. Tin and antimony are adsorbed in 10M HF while indium and manganese are eluted. In the second method the incident γ-ray intensity due to the tin matrix is reduced
by placing a lead absorber between the sample and the detector. The reproducibility and the sensitivity of both methods are
of the order of 10 ppb for manganese and of 1 ppb for indium for 1 g samples and a neutron flux of 1011 n·cm−2·sec−1.
Arsenic, selenium and antimony were determined in four different tin samples. After distillation from HBr−H2SO4 medium arsenic and selenium were precipitated with thioacetamide, and antimony was subsequently separated by deposition on
iron powder. The separated samples were counted on a high-resolution Ge(Li) γ-spectrometer. The sensitivity of the method
is highly satisfactory.
Neutron activation analysis for bismuth in lead was performed through the separation and measurement of210Po, using two different extraction procedures. The reproducibility of the results was good for lead containing bismuth in
higher concentrations. For high purity lead, variations in the bismuth content have been found by different analyses of the
same sample, owing to inhomogeneity in the distribution of the Bi metal traces. An independent analysis of the same lead samples
gave comparable Bi concentrations.