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?
As shown in the Figure below, the Se-82/Se-76 ratio varies from -1.2% to +0.2% for plant materials but remains relatively constant for other materials. The variations in plant material has been described as being due to differences in the bacteria residing in the plant. The question to investigate is whether or not these variations in the concentration can be used to determine the provenance of the sample.
Below is a table listing the natural abundances of Selenium
Natural abundance of selenium
Below are possible PAA reactions that may be used to observe specific Se isotopes
|Reaction||Half-life||Relative activity||Gamma-rays, keV (BR)|
|Se-74(gamma,n)Se-73||7.1 h||1.5E-1||361 (100)|
|Se-74(gamma,n)Se-73m||39 m||3.2||402 (4)|
|Se-74(gamma,np)As-72||26 h||1.0E-3||834 (100)|
Can one perform PAA measurements of Se-82 and Se-76?
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.
All runs lasting less than 214 seconds have time stamp that gives real time if you divide by clock frequency of 20 MHz. The first 32 bits are used for a real time measurement.
MDA and Se mass Calculations
IAC Detector Efficiencies
IAC Detector Calibrations
Goryachev, A. M., & Zalesnyy, G. N. (n.d.). The studying of the photoneutron reactions cross sections in the region of the giant dipole resonance in zinc, germanium, selenium, and strontium isotopes. Retrieved September 16, 2016, from http://www-nds.indcentre.org.in/exfor/servlet/X4sSearch5?EntryID=220070
Goryachev, B. I., Ishkhanov, B. S., Kapitonov, I. M., Piskarev, I. M., Piskarev, V. G., & Piskarev, O. P. (n.d.). Giant Dipole Resonance on Ni Isotopes. Retrieved October 26, 2016, from http://www-nds.indcentre.org.in/exfor/servlet/X4sGetSubent?reqx=119235&subID=220597006&plus=1
Handbook on Photonuclear data for applications, cross sections, and spectra. (2000, October). Retrieved November 4, 2016, from http://www-pub.iaea.org/MTCD/Publications/PDF/te_1178_prn.pdf