Spectral, nuclear, and matrix interferences in the determination of rare earths in geologic specimens by neutron activation analysis
- Univ. of Illinois, Urbana-Champaign (United States)
In the past, the study of the rare earths (lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium) has been of great interest to geochemists because of its petrogenic value. More recently rare earths have been used in a variety of geochemical prospecting techniques and source signatures in environmental studies. Perhaps one of the most common uses of instrumental neutron activation analysis (NAA) has been the determination of rare earths in geologic samples. Because of the relatively high activation cross section that these rare earths exhibit, analytical sensitivity for the majority of them is excellent, often with detection limits typically below one part per million. During the past decade, several papers have appeared on the nuclear interferences that uranium fission has on the determination of lanthanum, cerium, and neodymium. The spectral interferences of uranium, thorium, and gadolinium on samarium have also been tabulated. Although it is generally thought that matrix corrections are not needed for NAA, a very careful consideration must be given to self-absorption of gamma rays in high-Z materials. This is especially important when using the low-energy gamma rays of neutron-activated rare earths in geologic samples that contain high abundances of iron, nickel, lead, cobalt, etc. While this effect is small in typical silicate rocks, many different types of minerals have occlusions of such high-Z materials. This paper focuses on several important features of NAA of rare earths. These include preparation of primary standards, uranium fission interferences, spectral interferences including those often neglected, gamma-ray self-absorption, epithermal NAA to increase the sensitivity of certain elements, and the use of special instrumental techniques such as prompt-gamma, cyclic NAA, and Compton suppression.
- OSTI ID:
- 5933271
- Report Number(s):
- CONF-930601--
- Journal Information:
- Transactions of the American Nuclear Society; (United States), Journal Name: Transactions of the American Nuclear Society; (United States) Vol. 68; ISSN 0003-018X; ISSN TANSAO
- Country of Publication:
- United States
- Language:
- English
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ABSORPTION
ACTINIDES
ACTIVATION ANALYSIS
BASIC INTERACTIONS
CALIBRATION STANDARDS
CERIUM
CHEMICAL ANALYSIS
COBALT
COMPTON EFFECT
DYSPROSIUM
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GEOCHEMICAL SURVEYS
GEOLOGY
HOLMIUM
INTERACTIONS
INTERFERENCE
INTERFERING ELEMENTS
IONIZING RADIATIONS
IRON
LANTHANUM
LEAD
LUTETIUM
METALS
MINERALS
NEODYMIUM
NEUTRON ACTIVATION ANALYSIS
NICKEL
PETROLOGY
PRASEODYMIUM
PROMPT GAMMA RADIATION
PROSPECTING
RADIATIONS
RARE EARTHS
ROCKS
SAMARIUM
SCATTERING
SELF-ABSORPTION
SORPTION
STANDARDS
SURVEYS
TERBIUM
THORIUM
THULIUM
TRANSITION ELEMENTS
URANIUM
YTTERBIUM