Pulsed laser surface fragmentation and mid-infrared laser spectroscopy for remote detection of explosives

Stand-off technology for the remote detection of explosives and their traces on contaminated surfaces is a field of research that has recently gained much interest. Optical methods are well established in applications for counterterrorism because they facilitate analysis without contact between human being and hazardous materials. In this paper, to our knowledge for the first time, a remote stand-off detection system is developed by combination of pulsed laser fragmentation and pulsed mid-infrared laser absorption spectroscopy. Since the absorption of explosives is more efficient for infrared wavelengths laser radiation in the eye safe region around λ=1.47 μm rather than the conventional Nd:YAG laser line at λ=1.06 μm is preferred for the fragmentation. Generated product gases such as nitric oxide are probed by a synchronized distributed feedback quantum cascade laser (DFB-QCL) at λ≈5.3 μm. The ratio of NO and NO₂ is a measure to distinguish between energetic and non-energetic materials. PACS 42.62.Fi; 07.07.DF; 42.55.Px     

Synthèse dc la pyrido[2,3-f] phtalazine et des diformyl-6,7; -4,6; -4,7; -2,4 quinoleines

This article describes the synthesis of a new heterocycle, pyrido[2,3,f]phtalazine and three new diformylquinolincs.     

Synthèse des pyrido[2,3-d] el [3,2-d] -s-triazolo[3,4-f] pyrimidines el de (pyrazolyl-1')-4 pyrido[2,3-d] et [3,2-d] pyrimidines

The synthesis of two new heterocycles is described: pyrido-[2,3-d]-.s-triazolo[ 3,4-f] pyrimidine and pyrido[3,2-d]-.s-triayzolo-[3,4-f] pyrimidine. 4-[I'-Pyrazolyl]pyrido[2,3-d]pyrimidines and 4-[1′-pyrazoly1] pyrido[ 3,2-d] pyrimidine are obtained by the action of 4-hydrazinopyrido[2,3-d]pyrimidine and 4-hydrazinopyrido-[3,2-d]pyrimidine with several β-diketones.     

Stabilizing the Hammick intermediate

The possible stabilization of pyridine-2-ylidene has been investigated at B3LYP/6-31+G* and B3LYP/6-311+G** levels of theory. The aromaticity of this compound is a significant contributor to its stability (ISE(c) = 24-27 kcal mol(-1), Bird index = 77, NICS(0) = -6.8 ppm, NICS(1) = -9.1 ppm; all about 80% of those for the H-shift isomer pyridine). The stabilization energy of the carbene (measured by an appropriate isodesmic reaction) can be influenced by the substitution at nitrogen with bulky groups, and at the carbon atom by amino groups. Considering possible competitive deprotonation reactions of the most likely synthetic route, 1j, 1k, and 1L are suggested as synthesizeable new stable carbenes.     

N,N′‐Diorganylsubstituted Hydrazinium Azides

1,2‐Diorganylsubstituted derivatives of hydrazinium azide were examined in order to investigate their higher volatility and higher sensitivity to initiation compared to 1,1‐diorganylsubstituted hydrazinium azide derivatives. The compounds were synthesized from the respective hydrazines by reaction with HN₃ and characterized by elemental analysis, vibrational (IR, Raman) and multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁴N). Their sensitivity to friction, shock, electrostatic impact and heat was examined and the explosion products were investigated. The crystal structure of pyrazolidinium azide was determined.