implemented multivariate chemometric
analysis for classification using nanosecond LIBS data. 12-14
Myakalwar et al. have unambiguous-
ly established that even a small part of
the LIBS spectra (and not the entire spectra) is sufficient for explosives detection,
thereby reducing the computational anal-
ysis time when a large number of spectra
are utilized. 15 This same group has also
shown that non-gated detection is a pow-
erful tool for classification in the case of
pharmaceuticals, and has established the
effectiveness of LIBS techniques for fingerprinting of structural isomers—an important aspect of explosives detection. 16
The holy grail of worldwide standoff
explosives detection efforts is to develop
a portable system that unfailingly collects
LIBS data for various standoff distances,
can scan the target and operate in single
pulse mode to obtain signals from trace
samples in a short period of time, and
provide the least amount of false alarms.
Hybrid techniques such as LIBS-Raman
or nanosecond-femtosecond LIBS could
provide additional data-handling support
and improved detection. But for femtosec-
ond LIBS to meet niche applications for
standoff explosives detection, more research is required.
We would like to thank the Defence Research
Development Organization (DRDO) of India for
continued financial support. We also acknowledge Dr. S. Sreedhar for some of the femtosecond LIBS data, as well as the technical support
of Krishna Kumar and his team at LightMotif
(Hyderabad, India) for designing and delivering
the standoff optics.
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Shaik Abdul Kalam is a PhD student, Epuru
Nageswara Rao is research associate, and
Soma Venugopal Rao is professor, all in
the Advanced Centre of Research in High
Energy Materials (ACRHEM) at the University
of Hyderabad, Hyderabad, India; e-mail: