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We used an airborne Fourier transform infrared spectrometer (AFTIR), coupled to a flow-through, air-sampling cell, on a King Air B-90 to make in situ trace gas measurements in isolated smoke plumes from four, large, boreal zone wildfires in interior Alaska during June 1997. AFTIR spectra acquired near the source of the smoke plumes yielded excess mixing ratios for 13 of the most common trace gases: water, carbon dioxide, carbon monoxide, methane, nitric oxide, formaldehyde, acetic acid, formic acid, methanol, ethylene, acetylene, ammonia and hydrogen cyanide. Emission ratios to carbon monoxide for formaldehyde, acetic acid, and methanol were 2.2±0.4%, 1.3±0.4%, and 1.4±0.1%, respectively. For each oxygenated organic compound, a single linear equation fits our emission factors from Alaska, North Carolina, and laboratory fires as a function of modified combustion efficiency (MCE). A linear equation for predicting the NH3/NOx emission ratio as a function of MCE fits our Alaskan AFTIR results and those from many other studies. AFTIR spectra collected in downwind smoke that had aged 2.2±1 hours in the upper, early plume yielded ΔO3/ΔCO ratios of 7.9±2.4% resulting from O3 production rates of ∼50 ppbv h−1. The ΔNH3/ΔCO ratio in another plume decreased to 1/e of its initial value in ∼2.5 hours. A set of average emission ratios and emission factors for fires in Alaskan boreal forests is derived. We estimate that the 1997 Alaskan fires emitted 46±11 Tg of CO2.

Biomass burning is an important source of many trace gases in the global troposphere. We have constructed an airborne trace gas measurement system consisting of a Fourier transform infrared spectrometer (FTIR) coupled to a “flow-through” multipass cell (AFTIR) and installed it on a U.S. Department of Agriculture Forest Service King Air B-90. The first measurements with the new system were conducted in North Carolina during April 1997 on large, isolated biomass fire plumes. Simultaneous measurements included Global Positioning System (GPS); airborne sonde; particle light scattering, CO, and CO2; and integrated filter and canister samples. AFTIR spectra acquired within a few kilometers of the fires yielded excess mixing ratios for 10 of the most common trace gases in the smoke: water, carbon dioxide, carbon monoxide, methane, formaldehyde, acetic acid, formic acid, methanol, ethylene, and ammonia. Emission ratios to carbon monoxide for formaldehyde, acetic acid, and methanol were each 2.5±1%. This is in excellent agreement with (and confirms the relevance of) our results from laboratory fires. However, these ratios are significantly higher than the emission ratios reported for these compounds in some previous studies of “fresh” smoke. We present a simple photochemical model calculation that suggests that oxygenated organic compounds should be included in the assessment of ozone formation in smoke plumes. Our measured emission factors indicate that biomass fires could account for a significant portion of the oxygenated organic compounds and HOx present in the tropical troposphere during the dry season. Our fire measurements, along with recent measurements of oxygenated biogenic emissions and oxygenated organic compounds in the free troposphere, indicate that these rarely measured compounds play a major, but poorly understood, role in the HOx, NOx, and O3 chemistry of the troposphere.

The trace gas emissions from six biomass fires, including three grass fires, were measured using a Fourier transform infrared (FTIR) spectrometer coupled to an open-path, multipass cell (OP-FTIR). The quantified emissions consisted of carbon dioxide, nitric oxide, water vapor, carbon monoxide, methane, ammonia, ethylene, acetylene, isobutene, methanol, acetic acid, formic acid, formaldehyde, and hydroxyacetaldehyde. By including grass fires in this study we have now measured smoke composition from fires in each major vegetation class. The emission ratios of the oxygenated compounds, formaldehyde, methanol, and acetic acid, were 1–2% of CO in the grass fires, similar to our other laboratory and field measurements but significantly higher than in some other studies. These oxygenated compounds are important, as they affect O3 and HOx chemistry in both biomass fire plumes and the free troposphere. The OP-FTIR data and the simultaneously collected canister data indicated that the dominant C4 emission was isobutene (C4H8) and not 1-butene. The rate constant for the reaction of isobutene with the OH radical is 60% larger than that of 1-butene. We estimate that 67±9% of the fuel nitrogen was volatilized with the major nitrogen emissions, ammonia, and nitric oxide, accounting for 22±8%.

Mass-analyzed threshold ionization experiments have enabled mapping of the n -dependent Rydberg state survival probability for a series of molecules. Utilizing vacuum ultraviolet photons, one-photon Rydberg manifold spectra of Ar, HCl, N 2 , C 6 H 6 and O 2 were produced, and the prospects of photoinduced Rydberg ionization experiments examined. It was found that the widths of Rydberg manifolds for the molecules studied are quite different. Hydrogen chloride and nitrogen have the narrowest manifold width, followed by benzene, and then oxygen. These varying widths are most strongly correlated with the angular momentum (i.e., quantum defect) of the initially prepared Rydberg orbital.

Photoinduced Rydberg ionization (PIRI) spectroscopy has been applied to the problem of recording vibrationally resolved spectra of the dipole-forbidden B 2E2g←X 2E1g transition of C6H6+ and C6D6+. PIRI spectra of the B state have been recorded via a number of vibrational states of the ionic ground state. A combination of Herzberg–Teller and pseudo-Jahn–Teller vibronic coupling between the B state and a close lying C state were used to explain the complex B state vibrational structure. The two pseudo-Jahn–Teller vibrational modes, ν16 and ν17, were both found to be active in the PIRI spectra. In addition, evidence for a strong pseudo-Jahn–Teller interaction within each of these modes was found. The perturbed vibronic bands resulting from this pseudo-Jahn–Teller activity were successfully modeled using a two-mode pseudo-Jahn–Teller vibronic coupling model. Using a combination of the spectral results and the pseudo-Jahn–Teller calculations, we were able to generate absolute vibronic symmetry assignment...

In order to use segmented chemical flow processing in more complex reaction sequences, a method has been developed to precisely control the addition of reagent streams during multi-step operations. Using in-line infra-red monitoring with a new LabVIEW software application, it is possible to control additional pumps to dispense further reagents in real time based upon the concentration of reaction intermediates. This enables precise mixing with perfect timing thus greatly increasing product quality and enabling segmented chemical flow processing to be used in extended reaction sequences. © The Royal Society of Chemistry 2011.

A newly developed ReactIR flow cell is reported as a convenient and versatile inline analytical tool for continuous flow chemical processing. The flow cell, operated with ATR technology, is attached directly into a reaction flow stream using standard OmniFit (HPLC) connections and can be used in combination with both meso- and microscale flow chemistry equipment. The iC IR analysis software (version 4.0) enables the monitoring of reagent consumption and product formation, aiding the rapid optimisation of procedures. Short-lived reactive intermediates can also be observed in situ, giving further mechanistic insight into complex transformations.

A new method for the high‐resolution electronic spectroscopy of cations with mass resolution. Optical transitions from Rydberg states converging on the ground state of the cation to states with electronically excited cores are detected by their rapid autoionization. The spectrum of these transitions provide ionic information because the photoabsorption cross‐section of a molecule in a high‐n Rydberg state closely mirrors the spectrum of the ion core. The technique presented here, called photoinduced Rydberg ionization (PIRI) spectroscopy, is applied in this case to record the B 2E2g→X 2E1g transition of the benzene cation via the vibrational origin of the X 2E1g ionic state.

[1] We adopt a working definition of residual smoldering combustion (RSC) as biomass combustion that produces emissions that are not lofted by strong fire-induced convection. RSC emissions can be produced for up to several weeks after the passage of a flame front and they are mostly unaffected by flames. Fuels prone to RSC include downed logs, duff, and organic soils. Limited observations in the tropics and the boreal forest suggest that RSC is a globally significant source of emissions to the troposphere. This source was previously uncharacterized. We measured the first emission factors (EF) for RSC in a series of laboratory fires and in a wooded savanna in Zambia, Africa. We report EFRSC for both particles with diameter