Difference between revisions of "PAA Selenium"
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<math>{82 \atop 34\; }Se (\gamma,n){81 \atop \; }Se</math> | <math>{82 \atop 34\; }Se (\gamma,n){81 \atop \; }Se</math> | ||
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260 & 276 keV for the 57 minute half life isotope | 260 & 276 keV for the 57 minute half life isotope | ||
Revision as of 22:11, 7 March 2016
Using PAA ro measure Selenium concentrations.
According to Krouse<ref name="Krous1962"> H.R. Krause and H.G. Thode,"Thermodynamic Properties and Geochemistry of Iosotopic Compounds of Selenium",.Can. J. Chem., vol 40, pg 367</ref> , the fractional concentration of Se-82/Se-76 in plant material is observed to be less than from primordial (meteoric) concentrations by as much as 1.2%. Anaerobic bacteria are known to reduce selenates and senelites in biological systems. This may be the reason plant material has fractionation of selenium isotopes. They also observe excess concentrations of up to 0.4% in soil.
Plant material appears to detect environmental selenium.
Can one use plant material to measure the provenance of selenium?
Can one perform PAA measurements of Se-82 and Se-76?
Neutron knockout of Se-82
If you knock a neutron out of Se-82 you produce the unstable isotope Se-81 which Beta emitts with half life of 18 min and a meta-state that emmits a 103 keV gamma with a 57 minute half life.
Other prominent photons
260 & 276 keV for the 57 minute half life isotope
Neutron knockout of Se-76
If you knock a neutron out of Se-76 you produce the unstable isotope Se-75 which has a half life of 119 days.
The prominent photons emitted have the following energies
136, 264, and 279 keV
The article below describes how plant material and soil contain Se-76 to Se-82 ratios that differ from other natural samples by 1.5%. They argue that it is due to the bacteria living in plant material.
File:Krouse CanJournChem 40 1962 p367.pdf
Plant material is a natural way to sample the selenium content to determine if there are difference isotopic ratios due to the impact of human activities on the environment.
Experiments
First Observation of Se lines
Using the 44 Machine at 7 kW power and 44 meV incident electron energy to produce a bremsstrahlung spectrum with a mean energy of 15 meV.
References
<references/>
MSDS
Selenium shot, amorphous, 2-6 mm, Puratronic, 99.999% Alfa Aesar product # 10603 File:AlphaAesarSelenium MDSD.pdf
Informative links
https://inldigitallibrary.inl.gov/sti/3169894.pdf