[rjb]

Strange question and hopefully not too 'off topic'.

I'm not sure if many outside the UK will remember the death of Alexander Litvinenko (Wikipedia has a good page if not). He was a Russian ex-KGB agent and was poisoned in London (Nov 2006) with what was suspected to be Polonium-210 which was administered in a pot of tea served in a London hotel. He died 23 days after ingestion. During the investigation, it was stated that investigators were able to follow the 'radioactive trail' (and no doubt some CCTV evidence) left by the suspected assassin, which led them to a former Russian agent who had left from Heathrow airport on the day in question. Given that Po-210 is an alpha only emitter I was curious how following a 'radioactive trail' could practically be done. Using a G-M tube or similar doesn't seem a method likely to succeed given how easily alpha particles are stopped by air. Is anyone aware of an alternative technique that could be used at a greater distance?

Many thanks

R

[vmelkon]

I remember that case. They said they had to put him in a coffin with lead lining. As for the detection issue, I don't think they followed any path. I don't think there was a path of polonium in the streets to follow like a path of bread crums in Hunzle and Gretta.

[Peisander]

Isn't Polonium a highly reactive element in the presence of ionised energy? Surely one would just need to generate some Alpha radiation in the airliner's cabin and any tiny grains of Polonium would light up like a Christmas tree.

The chemical is used as a starter for neon tube lights exploiting this very fact. 

[rjb]

Peisander,

Interesting... I got a similar answer from a colleague, who, as it turns out was involved in projects researching the detection of radiological materials back in the 1970's. He mentioned something about a fluorescence technique, but didn't seem keen on elaborating, as seems to be his way! Any thoughts or ideas on how this this sort of approach could be implemented?

R

[vmelkon]

Isn't Polonium a highly reactive element in the presence of ionised energy? Surely one would just need to generate some Alpha radiation in the airliner's cabin and any tiny grains of Polonium would light up like a Christmas tree.

The chemical is used as a starter for neon tube lights exploiting this very fact. 

I don't know what you mean by ionised energy. Polonium is an alpha emitter.
Pure polonium glows because its radiation is intense and it ionizes the air.
If you had a low concentrated solution of polonium chloride, would you see a glow? Probably not.
I assume he sprayed the guy with a solution.
If the droplets landed somewhere and dried, would it glow? Would you see it?

[gippgig]

The polonium (whether a solid compound or liquid solution) was most likely poured, not sprayed, in the victim's drink. (I don't know if this has actually been determined.)

[Borek]

in the victim's drink

Tea, if I remember correctly.

[vmelkon]

Here is a picture of polonium, probably 210
http://gotexassoccer.com/elements/084Po/Po.htm

and a lot radium bromide (putting it here because it glows)
http://gotexassoccer.com/elements/088Ra/Ra.htm