VCU news

By Brian McNeill

The Department of Defense has awarded two grants totaling nearly $1.4 million to a Virginia Commonwealth University chemistry professor to study the initial steps of decomposition in “energetic molecules” that leads to explosions.

Katharine Moore Tibbetts, Ph.D., an assistant professor in the Department of Chemistry in the College of Humanities and Sciences, received a five-year, $1 million Army Research Office Early Career Award for Scientists and Engineers, as well as $335,000 from the Defense University Research Instrumentation Program to purchase equipment.

Tibbetts, who also received $60,000 last year from the Army Research Office to conduct initial research, is studying the dissociation dynamics of energetic molecules, which are chemical compounds used in explosives and propellants that have large amounts of energy stored in their chemical bonds.

The energy is released when the chemical bonds are broken during detonation of explosives and ignition of propellants. The goal of Tibbetts’ research is to identify the processes leading to the first bond-breaking event in energetic molecules that initiates detonation.

“The main reasons to study mechanisms of energetic molecule decomposition are to develop better methods for explosive detection and inform the design of new, better energetic molecules for particular applications,” Tibbetts said.

“For instance,” she said, “you might want to make a safer explosive by limiting unintended detonation, and a way to do this would be to have the energetic molecule making up the explosive able to initiate detonation only if it’s hit with a certain type of laser.”

The processes that induce bond breaking in energetic molecules can occur so fast they are measured in femtoseconds, or quadrillionths of a second (0.000000000000001 seconds).

To study these ultrafast processes, Tibbetts will use a pair of ultrashort pulse lasers to create a “camera” that captures the motions of individual energetic molecules on the femtosecond timescale.

The experiments will be performed on well-known explosives such as TNT and newly developed environmentally benign explosives such as biz-tetrazoles.

The results will have potential applications to both explosive detection and the design of novel energetic molecules with specified properties such as laser-initiated explosives.