Molecules with 100 or so electrons to annihilate faster

[talanum1]

I think the reason for molecules with 100 or so electrons to annihilate faster with a positron is because the electrons are quantum mechanicly smeared across a larger area.

 

[Bob S]

Positron lifetime is highest in polymers and insulators, shortest in metals. See slide 13 in
http://www.positronannihilation.net/Index_files/positron lifetime.pdf
Bob S

 

[Astronuc]

Positron lifetime is highest in polymers and insulators, shortest in metals. See slide 13 in
http://www.positronannihilation.net/Index_files/positron lifetime.pdf
Bob S

Polymers are mostly C_mH_n or C_mH_nO_p and insulators are metal oxides, usually richer in oxygen. C, H and O have relatively low electron density, as opposed to metals, from period 4 and greater, have much greater electron density - which means greater LET (linear energy transfer) or greater stopping power, and more electrons with which to annihilate