X-Ray Specs

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Scott Calvin (physics) discusses the finer points of diffractometry with Kirin Furst ’10, his research assistant, and Chauncy Yin ’13, whose conference project involves using the machine to look at the molecular structure of aspirin.You’re a scientist. You work with powders, crystals, and particles that are too tiny to be seen. How can you tell what they’re made of?

If you’re at Sarah Lawrence, you could use the x-ray diffractometer the College acquired over the summer. The machine shoots a beam of x-rays at a sample of the material, and records the pattern the rays make when they bounce off its surface. Since every substance diffracts x-rays differently, this pattern reveals the substance’s molecular structure.

A similar device was used to discover the double-helix shape of DNA, says physics faculty member Scott Calvin.

But that’s not all. The diffractometer can also be used to measure the size of particles that are narrower than a fine human hair. This semester, Calvin’s students will crush common crystals (like sugar) into a powder and measure them using the machine

“You can crush something to nanoparticle size”—that’s billionths of a meter—“using a mortar and pestle,” Calvin says. “People have been creating nanoparticles since ancient times. We just haven’t had a way to look at them until recently.” Thanks to this new machine, SLC physics students now have a way to take a closer look.

—Suzanne Walters Gray MFA ’04