Publications
Dynamic photoacoustic spectroscopy for trace gas detection
Summary
Summary
We present a method of photoacoustic spectroscopy in which a laser beam tuned to an absorption feature of a gas is swept through its plume at the speed of sound. The resulting coherent addition of acoustic waves leads to an amplification of the signal without the need for a resonant...
Noncontact optical detection of explosive particles via photodissociation followed by laser-induced fluorescence
Summary
Summary
High-sensitivity (ng/cm2) optical detection of the explosive 2,4,6- trinitrotoluene (TNT) is demonstrated using photodissociation followed by laser-induced fluorescence (PD-LIF). Detection occurs rapidly, within 6 laser pulses (~7 ns each) at a range of 15 cm. Dropcasting is used to create calibrated samples covering a wide range of TNT concentrations; and...
Noncontact detection of homemade explosive constituents via photodissociation followed by laser-induced fluorescence
Summary
Summary
Noncontact detection of the homemade explosive constituents urea nitrate, nitromethane and ammonium nitrate is achieved using photodissociation followed by laser-induced fluorescence (PD-LIF). Our technique utilizes a single ultraviolet laser pulse (~7 ns) to vaporize and photodissociate the condensed-phase materials, and then to detect the resulting vibrationally-excited NO fragments via laser-induced...
Measurement of trace explosive residues in a surrogate operational environment: implications for tactical use of chemical sensing in C-IED operations
Summary
Summary
A campaign to measure the amount of trace explosive residues in an operational military environment was conducted on May 27?31, 2007, at the National Training Center at Fort Irwin, CA, USA. The objectives of this campaign were to develop the methods needed to collect and analyze samples from tactical military...
A novel method for remotely detecting trace explosives
Summary
Summary
The development of a technique with the ability to detect trace quantities of explosives at a distance is of critical importance. In numerous situations when explosive devices are prepared, transported, or otherwise handled, quantifiable amounts of the explosive material end up on surfaces. Rapid detection of these chemical residues in...
Detection of condensed-phase explosives via laser-induced vaporization, photodissociation, and resonant excitation
Summary
Summary
We investigate the remote detection of explosives via a technique that vaporizes and photodissociates the condensed-phase material and detects the resulting vibrationally excited NO fragments via laser-induced fluorescence. The technique utilizes a single 7 ns pulse of a tunable laser near 236:2nm to perform these multiple processes. The resulting blue-shifted...
Experimental demonstration of remote optical detection of trace explosives.
Summary
Summary
MIT Lincoln Laboratory has developed a concept that could enable remote (10s of meters) detection of trace explosives' residues via a field-portable laser system. The technique relies upon laser-induced photodissociation of nitro-bearing explosives into vibrationally excited nitric oxide (NO) fragments. Subsequent optical probing of the first vibrationally excited state at...
Photoresist outgassing: a potential Achilles heel for short wavelength optical lithography?
Summary
Summary
The outgassing of volatile organic compounds during photoresist exposure at short wavelengths (