Naomi Ghahrai, Contributing Writer
The Department of Defense awarded $1.4 million to a VCU professor to expand her research on bombs — more specifically, the processes that start the chain reaction leading to detonation.
Using laser beams, chemistry professor Katharine Moore Tibbetts and her team of graduate students are looking at how bonds break before an explosive reaction happens. In February, they published a research article in the Journal of Physical Chemistry on the bond-breaking of 2-Nitrotoluene — a simpler version of TNT, which is an explosive molecule known as trinitrotoluene.
To capture the initial processes of the bond-breaking in the femtosecond, which is a quadrillionth of a second, scale, Tibbetts created a “camera” with two lasers. The molecule is shot with laser one, which is the start of the frame. Laser two — which represents the end of the frame — is then shot at the molecule. Tibbetts controls the time delay between laser one and two, allowing her to deduce what happened to the molecule in that small snapshot of time.
Research on explosives in computational chemistry — a branch of chemistry that uses computer simulation to solve chemical problems — has predicted which chemical bond in an explosive molecule will break and the amount of energy needed to break that bond. Moreover, many studies demonstrate “how explosives explode” or “what makes a good explosive,” but there is limited research on the very first processes of explosions, which are essential to understanding the start of the chain reaction leading to detonation.
Compared to other recent studies, Tibbetts uses laser pulses that are 10 times faster, allowing her to observe the moment before the chemical bonds break.
Tibbetts’ received $1 million of the total grant money from the Army Research Office Early Career Award for Scientists and Engineers. Another $335,000 came from the Defense University Research Instrumentation Program. Tibbetts said she plans to buy new equipment with the money.
“Currently, everything we are doing in our experiment is in the gas phase. This grant will help us work on other compounds that cannot evaporate,” said Derrick Ampadu-Boateng, a fourth-year chemistry graduate student working in Tibbetts’ laboratory.
Tibbetts said one implication of her research relates to accurately detecting explosives. Another application is the creation of more eco-friendly and safer explosives — for instance, she hopes her research will lead to the design of molecules that only detonate with a specific laser in order to prevent accidental explosions.
Tibbetts said her inspiration for her research stems from using the same ultrafast detection techniques in her research as a postdoctoral and graduate student years before joining VCU.
“Back then, we were just picking whatever molecule to see if it does anything interesting, but it is more fun if there is an application,” Tibbetts said. “So, I thought it would be cool if we could use my technique to learn something that is actually important.”
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