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 decay 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 3.6 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 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.

NAA result

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, the 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. Proton knockout directly goes to Pt-196 while neutron goes to this state through inverse beta decay (electron capture) of Au-196.

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

Neutron knockout

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

You could look for a coincidence between a 355.73 and 333.03 keV photon.

Coincidence signal

From http://radware.phy.ornl.gov/cgi-bin/cf

The coincidence 336->333 keV coincidence has a branching ration of 25% see ref. 2 below.

There is another coincidence for the case where the Gold is in an excited state after a neutron is knocked out. Two possible meta states exist with different half lives 8.6 second and 9.6 hours. The 8.6 second meta state emitts only one photon. The 9.6 hour meta state has 188 and 148 keV photons in coincidence.

The 188 and 148 keV photons are in coincidence

ref:

1.) Nucl.Phys. A796, 1 (2007), P.Petkov, J.Jolie, S.Heinze, S.E.Drissi, M.Dorthe, J.Groger, J.L.Schenker. "Nanosecond lifetimes and electromagnetic transition strengths in 196Au"

2.) Phys.Rev. C62, 064304 (2000), J.Groger, J.Jolie, R.Krucken, C.W.Beausang, M.Caprio, R.F.Casten, J.Cederkall, J.R.Cooper, F.Corminboeuf, L.Genilloud, G.Graw, C.Gunther, M.de Huu, A.I.Levon, A.Metz, J.R.Novak, N.Warr, T.Wende. "Nuclear Structure of 196Au: More evidence for its supersymmetric description"

There is also a coincidence signal for Pt-195 for 186 & 144 keV

Double neutron knockout

[math]{197 \atop\; }Au (\gamma,2n){195 \atop \; }Au[/math]

The meta state for two neutron knockout will emit several photons the dominant one is at 262 keV.

Au-195 will electron capture after 186 days to Pt-195 which has 186 and 144 keV lines in coincidence.

Proton knockout

Single proton knockout

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

double proton knockout

[math]{197 \atop\; }Au (\gamma,2p){195 \atop \; }Ir[/math]

Iridium has a meta state with a 3.8 hour half-life and it can Beta decay to Pt-195 with a half life of 2.5 hours. The Pt-195 can emit a 99 and 31 keV photons in coincidence.

Iridium CPAA

There are two naturally ocuring isotopes of iridium (37% Ir-191 and 63% Ir-193)

Neutron knockout can create Ir-190 and Ir-192.

Ir-190 has a half life of 11.78 days and decays to Os-190 via electron capture. The Os-190 state of 1.1631(4+) and 1.681 (5-) are the dominant final states. The 1.1631 state decays in 8.6 ps to the 2+ state of 557.9 keV emitting a 605 keV gamma which then decays to the ground state in 15.2 ps.

A coincidence between a 605 and a 557 gamma within a 50 ps window will mark this transition,.

Ir-192 has a half life of 73.8 days and beta decays to Pt-192. This half life is probably too long for a PAA analysis.

Gamma energy search

http://ie.lbl.gov/toi/radsearch.asp .

NAA

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 . The 8.1 second meta stable state decays by emitting a 85 keV ph0ton. 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.

PAA_Research