# Complex decay scheme

i am looking at the decay scheme of Sn126 > Sb 126 > Te126 and would like to know how many gamma rays Sb126 throws out on average and see if i've understood the diagram correctly;- Sn128 -> decays to (126m-Sb) 19.5min half life, where 14% decays through IT with 17.7 kev gamma and then 12.46 day half life 126 Sb. The other 86% of the isomer has 414.5kev, 666.1kev and 694.8kev gamma and various 1mev beta, according to (page 4). So only 14% goes through the 12 day decay scheme while the rest goes though a 19.5min decay scheme. What also confuses me is that is says 100% beta decay in the diagrams while there are tables for gamma emissions, is this for red numbers in the diagrams, occasional gamma emissions? eg p5
Also what is the average energy of beta given of and has anyone seen a more complex decay scheme?
thanks
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bcrowell
Staff Emeritus
Gold Member
Calculating the average gamma multiplicity is going to be complicated, because there are many branches in the 126Sb level-scheme. Note that if you were trying to detect these, many might be too low in energy to make it into your detector, so you wouldn't necessarily have any chance of detecting as many as there really are. In addition, the experimental multiplicity you'll see will be lower than the actual multiplicity because of some of the long half-lives, which won't let you see the whole chain in coincidence. The level scheme on p. 3 also seems to be incomplete, presumably due to experimental limitations; the intensities of the 88 keV and 23 keV gammas would have to sum to 100% if the level scheme were complete.

What also confuses me is that is says 100% beta decay in the diagrams while there are tables for gamma emissions, is this for red numbers in the diagrams, occasional gamma emissions?
Beta decay usually doesn't occur alone; usually it's followed by gamma decay. When they say it's 100% beta- decay, they mean that there is no decay through beta+ or internal conversion.

sorry, i meant Sb126m->Te126 decay, i read my post and see i didn't emphasize sb126m->Te126, i think the table and diagram for Sb126m are on p4 and Sb126 on page 5-6

also what do the symbols E, E, I, I, mean, (just under each table) and the red text for 414kev, 666.1kev and 694.8 kev energy
thank you
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