In reply to Eric Walker's message of Fri, 18 Dec 2015 20:00:39 -0600: Hi Eric, [snip] >On Fri, Dec 18, 2015 at 6:40 PM, <mix...@bigpond.com> wrote: > >While theoretically possible, consider that, if you are lucky, 1 in 10000 >> alphas >> would produce a nuclear reaction. 186W is only 28% of W. The amount of >> 190Os >> produced would be completely swamped by the existing W atoms. The same >> story >> goes for 194Pt, and even worse for 198Hg. In short I suspect you would be >> lucky >> to produce even a single Hg atom by this method. >> > >Note that we also have a path to 196Hg starting at 184W, which has a 30.64 >percent natural abundance, and to 194Hg (unstable) starting at 182W, which >has an abundance of 26.5, the three isotopes together comprising ~ 85 >percent of elemental tungsten.
Ok, there are more paths. > >To get a better sense of the level of your pessimism, consider the >improbable scenario where the alpha-capture cross section is temporarily >1e6 barns for the entire duration of the capacitor discharge, Why on Earth would one assume that? >on the same >order as the thermal neutron capture cross section for 135Xe. In this >scenario, do you think the final amount of Hg would still be unmeasurable? If one also assumes a significant number of alphas, probably not. > >In the link above, the mean weight of a tungsten wire in the experiment >was 0.713 mg, giving: > > (7.13e-4 g / 183.84 g/mol) * 6.022e23 atoms/mol = 2.34e18 atoms of W, Fine, but how many alphas are available? That's also going to determine the number of isotope atoms produced. Also the spatial distribution. If they are all produced at a single location, then you have a much better chance of a particular atom being hit multiple times. If they are produced randomly throughout the W, then the following calculation is a better guess. Given that a W atom needs to undergo 3 successive fusion reactions, the chances for it are the number of alphas divided by the number of W's * 0.85 * 1E-12 (I think I did that right), where 1E-12 is really just an educated guess. Furthermore, given that the fusion reactions are endothermic, the chances are probably vastly less than 1/10000 per reaction, and could be a little as 1 in millions. > >assuming pure tungsten. If you had to make a wild guess, what fraction of >that amount would need to be converted to Hg, by whatever route, in order >to appear in the line spectra they were looking at? Sorry, I have no idea, but I suspect that if you Google spectroscopy you may find out. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
