Quantitative and Sensitive Mid-Infrared Frequency Modulation Detection of HCN behind Shock Waves

Despite its key role for the study and modeling of nitrogen chemistry and NOx formation in combustion processes, HCN has only rarely been detected under high-temperature conditions. Here, we demonstrate quantitative detection of HCN behind incident and reflected shock waves using a novel sensitive single-tone mid-infrared frequency modulation (mid-IR-FM) detection scheme. The temperature-dependent pressure broadening of the P(26) line in the fundamental CH stretch vibration band was investigated in the temperature range 670K≤T≤1460K, yielding a pressure broadening coefficient for argon of 2γAr296K=(0.093±0.007)cm−1atm−1 and a temperature exponent of nAr=0.67±0.07. The sensitivity of the detection scheme was characterized by means of an Allan analysis, showing that HCN detection on the ppm mixing ratio level is possible at typical shock wave conditions. In order to demonstrate the capability of mid-IR-FM spectroscopy for future high-temperature reaction kinetic studies, we also report the first successful measurement of a reactive HCN decay profile induced by its reaction with oxygen atoms.

The Identification of Multiple Crystalline Zinc Soap Structures Using Infrared Spectroscopy

The formation of crystalline zinc soaps (zinc salts of fatty acids) in oil paint layers is a common sign of paint degradation. In this study, we have used infrared spectroscopy to systematically identify differences in structure and composition of crystalline zinc soap phases, and report data analysis methods for structure attribution in challenging oil paint samples. Supported by reported crystal structures, it was possible to distinguish two distinct types of zinc soap geometry: a highly symmetrical packing for long-chain saturated soaps (type B) and an alternating packing for zinc soaps with short, unsaturated, or dicarboxylic chains (type A). These two types of packing can be identified by a single or split asymmetric COO stretch vibration band. With this new information, we studied the structure and composition of zinc soaps formed in a zinc white model paint and in a cross-section from the painting Equations in Space by Lawren Harris. Using non-negative matrix factorization, band integration and band position maps, it was possible to clearly identify zinc azelate in the model paint and map its spatial distribution. The same methods showed that the paint cross-section contained both types of zinc soap structure within the same paint layer, with the less symmetrical structure appearing only at the interface with the ground layer. The results give valuable information on the internal chemistry of oil paint layers, and the demonstrated methods can find widespread application for in-depth analysis of infrared microscopy data.

Atomic Structure Modifications of Diamond-Like Nanocomposite Films: Observation by Raman Spectroscopy, FTIR and STM

ABSTRACTRaman spectroscopy, FTIR and scanning tunneling microscopy (STM) were used to study diamond-like nanocomposite (DLN) and metal containing DLN (Me-DLN) films. The FTIR spectra showed no appreciable absorption from the C-H stretch vibration band in DLN when 1 kV rf bias voltage was applied. Thermal annealing (450°C for 2 hrs) of (a) DLN and Cr-DLN films caused no change in the Raman spectra while (b) for Pt-DLN films there was a blue shift of both the crystalline (G) and microcrystalline (D) graphite-like features, an increase in the ID/IG intensity ratio and a decrease in the linewidths. The changes observed were more pronounced in the film with the highest Pt concentration. The STM image of this Pt-DLN film revealed a structure of aromatic graphite rings.

IR and Sims Study of Hydrogen Diffusion in RF Sputter Deposited Boron Doped a-Si:H and Undoped a-Ge:H

ABSTRACTSecondary ion mass spectrometry (SIMS) and IR measurements of long range deuterium motion in rf sputter deposited (rf sp) p-doped a-Si:H and undoped a-Ge:H are compared to recently published results on undoped rf sp a-Si:H, which exhibited strongly power-law time dependent diffusion constants (exponent α= 0.75±0.1) in films of as-deposited content of di-H and tri-H bonds (usually associated with microvoids) Ndo –4–5 at.%. In pdoped a-Si:H samples where Ndo-l.8–3.8at.%, the diffusion is much faster, but the exponent is similar. In undoped a-Ge:H exhibiting a stretch vibration band indicative of mono-H bonding only, the diffusion is about one order of magnitude faster than in undoped a-Si:H, and α = 0.23. The results are discussed in relation to both the multiple trapping (dispersive) and defect mediated diffusion models.