  We demonstrate single-beam coherent anti-Stokes Raman spectroscopy (CARS),
for detecting and identifying traces of solids, including minute amounts of
explosives, from a standoff distance (>50 m) using intense femtosecond pulses.
Until now, single-beam CARS methods relied on pulse-shapers in order to obtain
vibrational spectra. Here we present a simple and easy-to-implement detection
scheme, using a commercially available notch filter, that does not require the
use of a pulse-shaper.
