Spectroscopy Gauges Blast Potential

Stephanie A. Weiss

ATLANTA -- When FBI agents rush into the hideouts of terrorist groups, they often find jars of chemicals that could be explosive. Some explosives are so dangerous that they would be downright deadly under even the gentlest of jostling, so carrying them to a lab for analysis is out of the question.
Kevin McNesby of the US Army's Aberdeen (Md.) Proving Ground reported at Pittcon '97 that Raman spectroscopy can accurately assess an unknown material's explosive potential. The benefit of the technique is that agents could carry portable instruments and use a fiber probe to investigate their chemical finds without moving them.
McNesby said the military tests molecules' explosion potential by putting a sample on an anvil and dropping a weight on it. Researchers study the size of the resulting flash and the amount of energy that was required to produce it.
McNesby found that Raman spectroscopy can accurately predict which molecules will explode most efficiently by determining the number of Raman peaks from 100 to 700 cm²¹. More peaks mean more transition states, which calculate to more volatility. For example, he said, the explosive beta-HMX has far fewer peaks in this region than its extremely volatile (and dangerous) relative, gamma-HMX.
He said the technique could prevent disastrous accidents during law enforcement raids and could greatly simplify the research and design of new explosive materials.