Message:

<p>[QUOTE=&quot;Colonialjohn, post: 2135368, member: 57741&quot;]Bajjerfan - a production by-product on the surface is respectable enough. The high vacuum is required in XPS is needed so the lighter elements like chlorine and sulfur can be measured like in a SEM/EDS analysis. It really has nothing to do with how clean or dirty the surface of a coin is prior to analysis. Certain coins are polished to get a more represenative alloy under the aged patina. To measure using XPS it needs to be done in a vacuum so the lighter elements do not impart false readings on the heavier metals like silver.</p><p><br /></p><p>But remember your toned Morgan Dollar in your pic is PMD with atmospheric sulfur as described per White&#039;s Coin Chemistry book - as simple as that treatise was with this collector. Your one? XPS witness test I guess prevents you to also visualize chlorine as another atmospheric contaminant or another form of PMD.</p><p><br /></p><p>XPS is a surface chemical analysis technique that can be used to analyze the <a href="http://en.wikipedia.org/wiki/Surface_science#Surface_chemistry" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://en.wikipedia.org/wiki/Surface_science#Surface_chemistry" rel="nofollow">surface chemistry</a> of a material in its as-received state, or after some treatment, for example: fracturing, cutting or scraping in air or UHV to expose the bulk chemistry, <a href="http://en.wikipedia.org/wiki/Ion_beam#Ion_beam_etching_or_sputtering" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://en.wikipedia.org/wiki/Ion_beam#Ion_beam_etching_or_sputtering" rel="nofollow">ion beam etching</a> to clean off some or all of the surface contamination (with mild ion etching) or to intentionally expose deeper layers of the sample (with more extensive ion etching) in depth-profiling XPS, exposure to heat to study the changes due to heating, exposure to reactive gases or solutions, exposure to <a href="http://en.wikipedia.org/wiki/Ion_implantation" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://en.wikipedia.org/wiki/Ion_implantation" rel="nofollow">ion beam implant</a>, exposure to <a href="http://en.wikipedia.org/wiki/Ultraviolet_light" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://en.wikipedia.org/wiki/Ultraviolet_light" rel="nofollow">ultraviolet light</a>.</p><p><br /></p><p>John Lorenzo</p><p>Numismatist</p><p>United States[/QUOTE]</p><p><br /></p>

Your name or email address:

Do you already have an account?

• No, create an account now.
• Yes, my password is:
• Forgot your password?

Stay logged in