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[Phys-l] Isotope chemistry and physics



John;

I believe slight differences in isotope mass are used in ice core samples as a proxy for temperature fluctuations. Warmer climates favor the evaporation of D2O resulting in a larger accumulation of this isotope in ice formed from snow accumulation during that year. Oxygen and nitrogen isotopes are used in a similar fashion as temperature proxies. This is a key piece of our understanding of ice age cycles over the past 800,000 years.

kyle


Message: 1
Date: Sun, 15 Mar 2009 10:20:26 -0600
From: "John SOHL" <jsohl@weber.edu>
Subject: [Phys-l] Isotope chemistry and physics
To: <phys-l@carnot.physics.buffalo.edu>
Message-ID: <49BCD66A.6268.00E4.0@weber.edu>
Content-Type: text/plain; charset=US-ASCII

In a recent post on climate change and CO2 the link:
http://www.realclimate.org/index.php?p=87
was posted as evidence of the anthropomorphic source of carbon in the fraction of greenhouse gasses that are the increase from historic levels.

In that link they state that we know the source "because plants have a preference for the lighter isotopes (C-12 vs. C-13); thus they have lower C-13/C-12 ratios."

** WHAT???!! **

I was confused here. I was always under the impression that chemical processes were pretty much totally independent of isotopic content and mostly a matter of interactions with outer shell electrons. End of story. After all, if we could chemically manipulate isotopes then making nuclear fuel/explosives would be a lot easier. (I'm not thinking here of things like using isotopically prepared chemicals as things like tracers and the like. That is all nuclear physics.)

So, a few seconds with Google, proving that my personal first steps in learning are not by inquiry methods :-), produced:
http://www.bnl.gov/chemistry/History/IsotopeChemistry.asp
It makes sense to me, now in retrospect, that the small isotopic shifts in energy levels might have a tiny but uniformly detectable effect on complex chemical processes such as photosynthesis. I had never thought about it before, even though I can spectroscopically detect these shifts in my own lab.

So now I have to wonder how many other natural processes are (slightly) isotopically dependent. What other cool secrets we can coax out of the universe with such a fingerprint?

Scientific sleuthing! I love it. It always amazes me that with the wonderful complexities and curiosities of the universe that people have to make up stuff like astrology and crystal power.

All the best,

John

P.S. Despite the tongue-in-cheek comment above about not starting with inquiry, my personal approach to many things, such as electronics, computer programming, plumbing and auto repair, is to read a tiny bit then just go fool around with it. The inquiry approach in its full glory. :-)



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John E. Sohl, Ph.D.
Professor of Physics
Weber State University
2508 University Circle
Ogden, UT 84408-2508

--
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"When applied to material things,
the term "sustainable growth" is an oxymoron."
Albert Bartlett

kyle forinash 812-941-2039
kforinas@ius.edu
http://Physics.ius.edu/
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