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\title{ACS AMA: We're James Patterson and Shawn Averett from Brigham Young
University. Ask us anything about using lasers for non-destructive
testing of structures.}



\author[1]{AmerChemSocietyAMA }%
\author[1]{r/Science AMAs}%
\affil[1]{Affiliation not available}%


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  \date{April 23, 2026}


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\begin{abstract}
ACS AMA Hello, Reddit! I'm Prof. James E. Patterson of Brigham Young
University. I completed my B.S. and M.S. degrees in chemistry at BYU,
and my Ph.D. in physical chemistry at the University of Illinois at
Urbana-Champaign. After a postdoctoral fellowship at the Institute for
Shock Physics at Washington State University, I began my appointment at
BYU in 2007. Most of my work has focused on the use of nonlinear optics
(sum-frequency generation and second harmonic generation) to the
molecular-level investigation of materials and interfaces. A common
theme has been to understand the molecular response of materials, such
as polymers and metals, to mechanical, thermal and chemical stress. Hi
Reddit! My name is Shawn Averett, and I am finishing a Ph.D. in physical
chemistry at BYU. As a graduate student I use sum frequency generation
spectroscopy to investigate the surface response of materials to
mechanical deformation. I am also working to better understand the
nature and origin of nonresonant sum frequency generation. Prior to
graduate school I taught high school science and engineering for four
years. Our team recently presented research about a new laser-based
technique we've developed to reveal hidden damage in metals at the 253rd
American Chemical Society National Meeting \& Exposition.
Non-destructive testing (or NDT) offers the ability to check the
structural integrity of an airplane, ship, or bridge without having to
dismantle it or remove any material for testing, which could further
compromise the structure. Current NDT techniques include X-ray imaging,
which can detect microscopic cracks in metals. This method is expensive,
requires shielding from the X-rays, and is difficult to use in the
field. Other NDT techniques give less precise results and require highly
trained technicians. Our approach uses a spectroscopic method known as
second harmonic generation (SHG), which alters the wavelength of the
light. We start with shining green laser light onto a metal sample.
Through SHG, the metal converts some of the incoming light into
ultraviolet light, which bounces back from the metal along with the
remaining green light. By measuring this conversion, we can detect if
the metals have been changed by some form of stress. We've found this
technique can distinguish between metal samples that are still sound and
those that have been irreversibly damaged and require replacing. Our
method can detect damage invisible to current NDT, and because SHG is
extremely sensitive to material changes it may give earlier warning of
danger for damage that current NDT can detect. You can learn more about
this research in this video. Ask us anything about our new approach for
non-destructive testing and its applications for detecting damage. We'll
be back at 11am EDT (8am PDT, 3pm UTC) to answer your questions! -acs
edit%
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