Shards of Glass and Extreme Temperatures

Special Summer Series: Elizabeth Hoover de Galvez from the library's reference department, shares her observations of summer research at Coe. This summer she is working with Dr. Feller's materials science group.

The physics labs on campus are a foreign world where multiple furnaces glow orange at 1800 degrees Fahrenheit, glass is crushed into a powder with shards flying, and liquid nitrogen is pumped from large tanks into instruments where air won't suffice.  It's a place where cosmic rays become visible as sudden peaks on a graph and an electron microscope provides a window to the unimagined textures and structures of the nano-world.

Raman spectrum from a sample of .4 Sodium Borate glass.
The peaks at 771 cm-1 and 498 cm-1 are due, respectively, to the
"breathing" and back and forth vibrations
of the 3,4 coordinated rings.  The hump at 1385 cm-1 is due
to the vibrations of non-bridging oxygens.
Whatever that all means...

To me, it sounds fairly poetic to imagine a molecule breathing, but that is exactly how Dr. Feller describes the structural vibrations of one type of glass, which is apparently evident from the spectrum shown at right.  He explains how the Raman spectroscopy works.  First the machine sends out a laser beam which hits the glass and spreads out over the surface.  Don't quote me on this, but I believe the laser itself is responsible for exciting the molecules so they start vibrating in a new way, as does the beam of laser light.  All of these vibrations, though, are constrained by the structure of the molecules, so the location, height, and steepness of the peaks in the resulting spectrum graph provide clues to the molecules structure.

After skimming through the Wikipedia entries on Raman, spectroscopy, and inelastic scattering, I'm still fairly confused about how all this works...just as I was over 10 years ago when I initially learned about spectroscopy.  But the students don't seem confused--at the first meeting, they were conjecturing about the reasons for the locations of the peaks and asking questions about the slope of the peaks, which seemed to impress Dr. Feller quite a bit.  It's nice to be the outsider who isn't expected to understand everything...far more enjoyable that way.