Thursday, 16 August 2012

Working in Montréal today --I WAS WRONG, BRIAN WAS RIGHT

Good morning folks,  I will be working in Montréal today.


Last night my friend Brian, while having beer after Racquetball, had made a remark about Canadian diamonds being inscribed with a polar bear to specifically identify as Canadian as apposed to diamonds mined by oppressive regimes and slave labour.  I thought hmmm...  

I am not a gemologist, although I have played one on TV, but my understanding of diamond cutting was that one involves cleaving off whole facets into the desired shape and then polishing the surface with other diamonds.  So I queried Brian on the method, and he said, "lasers".

Right, I thought, 'lasers' the answer that everyone spits out when they don't know.  My doubt was that my understanding was that lasers passed through a diamond without exciting any of the carbon atoms.  My doubt did not reach a full heckling of Brian's assertion, but I did express it with a certain degree of pub table confidence, however I did promise to do a bit of research on this and figure out how this could be and report here if it indeed could be.

I finished my beer, went straight home, started to read about diamonds, wavelengths, lasers, ablation, and promptly fell asleep.  Here I am at 27,000 feet and will attempt to recall what I learned.

Lasers generally are ineffective at affecting diamonds.  But!  That is because most lasers are in the spectrum range from the bottom of visible light right up through far infrared.  These lights all pass through diamonds.  Yes, I wish I could stop right about here.. But sadly.. No.

There are a number of lasers that emit light in the near (300-400 nm), middle (200-300 nm) and far ultraviolet(122-200 nm) ranges.  I know of no lasers that emit light in the extreme or vacuum UV range but the next wavelengths are X-rays and we have plenty of machines that emit energy in that frequency range.

Sorry, got carried away.  It turns out that light in the far UV, actually very far < 200 mn can excite carbon atoms on the surface of a diamond, destroy the bond with their neighboring atoms and result in ablation.  For those of you that are curious and not just reading this out of sheer politeness the rate of ablation is reportedly 1 carbon atom abated per two photon's energy absorbed.

I guess I was wrong and Brian was right.  I WAS WRONG - BRIAN WAS RIGHT.  Bastard.

Have a good day anyway.

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