DeepBlueMarine Physics

Ancient Silver

File:Meyers Zelst Sayre BNL-21513.pdf This paper suggest that the gold and iridium content can be used to distinguish between Sasanian (Iran) coins and other silver coins.

Activating gold

Neutron knock out

[math]{197 \atop\; }Au (\gamma,n){196 \atop \; }Au[/math]

Au-196 decays with a half life 6.183 days of by electron capture to Platinum (Pt-196) 92% of the time or the rest of the time it Beta decay to Hg-196

The highest relative intensity gamma ray has an energy of 333.03 keV after Au-196 undergoes electron capture. Pt-196 is stable.

If Pt-196 is in an excited state, then there are two lifetimes to de-excite of 8.1 seconds and 9.6 hours . For the 9.6 hours state then dominant intensities are a photon emission energies of 188.27 and 147.81 keV.

Proton Knockout

[math]{197 \atop\; }Au (\gamma,p){196 \atop \; }Pt[/math]

Pt-196 is naturally occurring in 25% of the Platinum

You will need to produce it in an excited state (356, 689, 877,1526 keV) in order to get a gamma.

Activation Iridium

There are two naturally occuring isotopes of Iridium (37% Ir-191, 63%Ir-193)

Neutron knock out

[math]{191 \atop\; }Ir (\gamma,n){190 \atop \; }Ir[/math]

After 11.78 days Ir-190 electron captures to Os-190 (dominant decay) with the most intense line emission of 186.68 keV.

Proton knock out

[math]{191 \atop\; }Ir (\gamma,n){190 \atop \; }Os[/math]

[math]{193 \atop\; }Ir (\gamma,n){192 \atop \; }Os[/math]

Osmium 192 and 190 are stable.

Coincidence PAA

The NAA analysis suggests that Gold and Iridium are useful for distinguishing between silver coins

Gold CPAA

PAA_Research