DeepBlueMarine Physics

Ancient Silver

Activating Silver

If you knock a neutron out of Ag-107 making Ag-106

[math]{107 \atop\; }Ag (\gamma,n){106 \atop \; }Ag[/math]

Ag-106 will decays 92% of the time to the 5+ (2757 keV) state of Palladium Pd-106 after 8 days giving off an 89.66 keV gamma. The 2757, 5+ state of Pd-106 decays with a half life less than 3.2 ns. The most prominent photon line from this is at 450.97 keV. If Pd-106 gives off a 450.97 keV photon, it will be in the 2305.62 keV energy state for a half life of 2 ns. The 2305.62 energy state's will most likely emit a 748.44 keV photon and end up in the 1557.68 keV energy state. It will stay in the 1557.68 keV energy state for several ps and then emit a 1045.84 keV photon on its way to the 511 energy level which will then decay with a half life of 12 ps.

The coincidence experiment can then be to look for photons that are in time with the 511 photons. You could see photons with energies of 450.97, 748.44, or 1045.84 keV.

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

Both neutron and proton knockout to Platinun-196

[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.

There are two dominant photon energies of 333.03 keV and 355.73 keV. 67% of the time Au-196 goes to the 2+ excited state of Pt-196 after 34.15 ps . 24.7% of the time it decays to the next higher energy 2+ state of Pt-196 after 33.8 ps and then proceeds to emitt a 333.03 keV photon as it transitions to the lower 2+ state where it will emitt a 355.73 keV photon on its way to the ground state.

http://www.nndc.bnl.gov/nudat2/getdataset.jsp?nucleus=196PT&unc=nds

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

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

PAA_Research