<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi Andrew and all,<div class=""> Below is a pdf copy of the article <a href="https://www.researchgate.net/publication/235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold" target="_blank" class="">https://www.researchgate.<wbr class="">net/publication/235335367_The_<wbr class="">Miracle_of_the_Electron-<wbr class="">Positron_Pair_Production_<wbr class="">Threshold</a> with the abstract (below) you are quoting from. Definitely the minimum incoming photon energy is much less than 2 MeV and much nearer to the quoted value. It turns out that it’s very hard (as explained in the article) to experimentally confirm the minimum photon energy value for a particular recoil nuclear mass, given by the formula, so there’s surprisingly much experimental (and perhaps theoretical also) work still needed on this relatively straightforward conversion process of a photon to an electron-positron pair.</div><div class=""> Richard</div><div class=""></div></body></html>