Quantum monodromy in NCNCS - direct experimental confirmation.

Since the first confirmation of quantum monodromy in NCNCS (B. P. Winnewisser , Report No.

Enhanced MMW and SMMW/THz imaging system performance prediction and analysis tool for concealed weapon detection and pilotage obstacle avoidance.

The U.S. Army Research Laboratory has continued to develop and enhance a millimeter-wave (MMW) and submillimeter-wave (SMMW)/terahertz (THz)-band imaging system performance prediction and analysis tool for both the detection and identification of concealed weaponry and for pilotage obstacle avoidance.

Indirect ignition of energetic materials with laser-driven flyer plates.

The impact of laser-driven flyer plates on energetic materials CL-20, PETN, and TATB has been investigated. Flyer plates composed of 25 μm thick Al were impacted into the energetic materials at velocities up to 1.3 km/s.

Range resolved mode mixing in a large volume for the mitigation of speckle and strategic target orientation requirements in active millimeter-wave imaging.

In spite of many reports of active millimeter-wave imaging in the literature, speckle and requirements for cooperative target orientation significantly reduce its practical usefulness. Here we report a new technique, range resolved mode mixing (RRMM), which significantly mitigates both of these issues. It also provides a three-dimensional (3D) image.

Multimode illumination for speckle reduction and angle neutrality in millimeter wave active imaging: range and time-resolved mode averaging.

Active illumination is an attractive approach for millimeter and submillimeter wave imaging because of its generally larger signal margins and capacity for range determination. However, the resultant speckle from diffuse targets and the requirement that specular targets have strategic angular alignment are significant shortcomings. As a result, many, if not most, demonstrations of active imaging have involved the use of strategically oriented specular targets.

Pursuit of quantum monodromy in the far-infrared and mid-infrared spectra of NCNCS using synchrotron radiation.

Quantum monodromy has a dramatic and defining impact on all those physical properties of chain-molecules that depend on a large-amplitude bending coordinate, including in particular the distribution of the ro-vibrational energy levels. As revealed by its pure rotational (a-type) spectrum [B. P.

Far-infrared spectrum of S(CN)2 measured with synchrotron radiation: global analysis of the available high-resolution spectroscopic data.

The high resolution Fourier transform spectrum of the chemically challenging sulfur dicyanide, S(CN)2, molecule was recorded at the far-infrared beamline of the synchrotron at the Canadian Light Source. The spectrum covered 50-350 cm(-1), and transitions in three fundamentals, ν4, ν7, and ν8, as well as in the hot-band sequence (n + 1)ν4 - nν4, n = 1-4, have been assigned and measured. Global analysis of over 21,300 pure rotation and rotation vibration transitions allowed determination of precise energies for 12 of the lowest vibrationally excited states of S(CN)2, including the five lowest fundamentals.

Influence of molecular structure on the laser-induced plasma emission of the explosive RDX and organic polymers.

A series of organic polymers and the military explosive cyclotrimethylenetrinitramine (RDX) were studied using the light emission from a femtosecond laser-induced plasma under an argon atmosphere. The relationship between the molecular structure and plasma emission was established by using the percentages of the atomic species (C, H, N, O) and bond types (C-C, C═C, C-N, and C≡N) in combination with the atomic/molecular emission intensities and decay rates. In contrast to previous studies of organic explosives in which C2 was primarily formed by recombination, for the organic materials in this study the percentage of C-C (and C═C) bonds was strongly correlated to the molecular C2 emission.

Elimination of speckle and target orientation requirements in millimeter-wave active imaging by modulated multimode mixing illumination.

Active imaging can provide significantly larger signal margins in the millimeter-wave spectral region than passive imaging, especially indoors-an important application for which there is no cold sky illumination. However, coherent effects, such as speckle, negate much of this advantage by destroying image clarity and target recognition. Moreover, active imaging demonstrations often use strategically chosen target orientations to optimally reflect power from the active illuminator back to the imaging receiver.

Classification of explosive residues on organic substrates using laser induced breakdown spectroscopy.

Standoff laser induced breakdown spectroscopy (LIBS) has previously been used to classify trace residues as either hazardous (explosives, biological, etc.) or benign. Correct classification can become more difficult depending on the surface/substrate underneath the residue due to variations in the laser-material interaction.

Impact of atmospheric clutter on Doppler-limited gas sensors in the submillimeter/terahertz.

It is well known that clutter (spectral interference) from atmospheric constituents can be a severe limit for spectroscopic point sensors, especially where high sensitivity and specificity are required. In this paper, we will show for submillimeter/terahertz (SMM/THz) sensors that use cw electronic techniques the clutter limit for the detection of common target gases with absolute specificity (probability of false alarm ≪ 10⁻¹⁰) is in the ppt (1 part in 10¹²) range or lower. This is because the most abundant atmospheric gases are either transparent to SMM/THz radiation (e.

Determination of precise relative energies of conformers of n-propanol by rotational spectroscopy.

The rotational spectrum of n-propanol (n-CH(3)CH(2)CH(2)OH) was studied with several techniques of contemporary broadband rotational spectroscopy at frequencies from 8 to 550 GHz. Rotational transitions in all five conformers of the molecule, Gt, Gg, Gg', Tt, and Tg, have been unambiguously assigned. Over 6700 lines of the Gt, Gg, and Gg' species, for quantum number values reaching K(a) = 33 and J = 67, were fitted in a joint analysis leading to the determination of DeltaE(Gg-Gt) = 47.

Submillimeter spectroscopy for chemical analysis with absolute specificity.

A sensor based on rotational signatures in the submillimeter (SMM) region is described. This sensor uses frequency synthesis techniques in the region around 10 GHz, with nonlinear diode frequency multiplication to 210-270 GHz. This provides not only a nearly ideal instrument function, but also frequency control and agility that significantly enhance the performance of the spectrometer as a sensor.

Analysis of the FASSST rotational spectrum of NCNCS in view of quantum monodromy.

Quantum monodromy has a strong impact on the ro-vibrational energy levels of chain molecules whose bending potential energy function has the form of the bottom of a champagne bottle (i.e. with a hump or punt) around the linear configuration.

Laser-induced breakdown spectroscopy for detection of explosives residues: a review of recent advances, challenges, and future prospects.

In this review we discuss the application of laser-induced breakdown spectroscopy (LIBS) to the problem of detection of residues of explosives. Research in this area presented in open literature is reviewed. Both laboratory and field-tested standoff LIBS instruments have been used to detect explosive materials.

Evaluation of femtosecond laser-induced breakdown spectroscopy for explosive residue detection.

Recently laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential technique for trace explosive detection. Typically LIBS is performed using nanosecond laser pulses. For this work, we have investigated the use of femtosecond laser pulses for explosive residue detection at two different fluences.

Laser-induced breakdown spectroscopy for the classification of unknown powders.

Laser-induced breakdown spectroscopy (LIBS) was used to discern between two biological agent surrogates (Bacillus atrophaeus and ovalbumin) and potential interferent compounds (mold spores, humic acid, house dust, and Arizona road dust). Multiple linear regression and neural network analysis models were constructed by using B. atrophaeus and ovalbumin spectra, and limits of detection were calculated.

Use of laser induced breakdown spectroscopy in the determination of gem provenance: beryls.

The provenance of gem stones has been of interest to geologists, gemologists, archeologists, and historians for centuries. Laser induced breakdown spectroscopy (LIBS) provides a minimally destructive tool for recording the rich chemical signatures of gem beryls (aquamarine, goshenite, heliodor, and morganite). Broadband LIBS spectra of 39 beryl (Be(3)Al(2)Si(6)O(18)) specimens from 11 pegmatite mines in New Hampshire, Connecticut, and Maine (USA) are used to assess the potential of using principal component analysis of LIBS spectra to determine specimen provenance.

Detection of indoor biological hazards using the man-portable laser induced breakdown spectrometer.

The performance of a man-portable laser induced breakdown spectrometer was evaluated for the detection of biological powders on indoor office surfaces and wipe materials. Identification of pure unknown powders was performed by comparing against a library of spectra containing biological agent surrogates and confusant materials, such as dusts, diesel soot, natural and artificial sweeteners, and drink powders, using linear correlation analysis. Simple models constructed using a second technique, partial least squares discriminant analysis, successfully identified Bacillus subtilis (BG) spores on wipe materials and office surfaces.

Multivariate analysis of standoff laser-induced breakdown spectroscopy spectra for classification of explosive-containing residues.

A technique being evaluated for standoff explosives detection is laser-induced breakdown spectroscopy (LIBS). LIBS is a real-time sensor technology that uses components that can be configured into a ruggedized standoff instrument. The U.

Terahertz imaging system performance model for concealed-weapon identification.

The U.S. Army Night Vision and Electronic Sensors Directorate (NVESD) and the U.

Standoff detection of chemical and biological threats using laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for real-time chemical and biological warfare agent detection in the field. We have demonstrated the detection and discrimination of the biological warfare agent surrogates Bacillus subtilis (BG) (2% false negatives, 0% false positives) and ovalbumin (0% false negatives, 1% false positives) at 20 meters using standoff laser-induced breakdown spectroscopy (ST-LIBS) and linear correlation. Unknown interferent samples (not included in the model), samples on different substrates, and mixtures of BG and Arizona road dust have been classified with reasonable success using partial least squares discriminant analysis (PLS-DA).

Chemical analysis in the submillimetre spectral region with a compact solid state system.

A new analytical system that uses the rotational signatures of gas phase molecules is described and demonstrated. It uses a solid state source to probe molecular systems in the millimetre and submillimetre wave range, the only region of the electromagnetic spectrum not yet used extensively for analytical purposes. It employs the FAst Scan Submillimetre Spectroscopy Technique (FASSST), which leads to an especially simple system architecture.

LIBS for landmine detection and discrimination.

The concept of utilizing laser-induced breakdown spectroscopy (LIBS) technology for landmine detection and discrimination has been evaluated using both laboratory LIBS and a prototype man-portable LIBS systems. LIBS spectra were collected for a suite of landmine casings, non-mine plastic materials, and "clutter-type" objects likely to be present in the soil of a conflict area or a former conflict area. Landmine casings examined included a broad selection of anti-personnel and anti-tank mines from different countries of manufacture.

Laser-induced breakdown spectroscopy analysis of complex silicate minerals--beryl.

Beryl (Be3Al2Si6O18) is a chemically complex and highly compositionally variable gem-forming mineral found in a variety of geologic settings worldwide. A methodology and analytical protocol were developed for the analysis of beryl by laser-induced breakdown spectroscopy (LIBS) that minimizes the coefficient of variance for multiple analyses of the same specimen. The parameters considered were laser energy/pulse, time delay and crystallographic orientation.