Six different chiral and achiral alkane dicarboxylic C₄-acids resulted in the formation of Ce(iv)-MOFs crystallizing in three different framework topologies.

A detailed mechanism for the thermal decomposition and oxidation of the flame intermediate glyoxal (OCHCHO) has been assembled from available theoretical and experimental literature data. The modeling capabilities of this extensive mechanism have been tested by simulating experimental HCO profiles measured at intermediate and high temperatures in previous glyoxal photolysis and pyrolysis studies. Additionally, new experiments on glyoxal pyrolysis and oxidation have been performed with glyoxal and glyoxal/oxygen mixtures in Ar behind shock waves at temperatures of 1285–1760 K at two different total density ranges. HCO concentration–time profiles have been detected by frequency modulation spectroscopy at a wavelength of λ = 614.752 nm. The temperature range of available direct rate constant data of the high-temperature key reaction HCO + O₂ → CO + HO₂ has been extended up to 1705 K and confirms a temperature dependence consistent with a dominating direct abstraction channel. Taking into account available literature data obtained at lower temperatures, the following rate constant expression is recommended over the temperature range 295 K < T < 1705 K: k₁/(cm³ mol^–1 s^–1) = 6.92 × 10⁶ × T^1.90 × exp(+5.73 kJ/mol/RT). At intermediate temperatures, the reaction OCHCHO + HO₂ becomes more important. A detailed reanalysis of previous experimental data as well as more recent theoretical predictions favor the formation of a recombination product in contrast to the formerly assumed dominating and fast OH-forming channel. Modeling results of the present study support the formation of HOCH(OO)CHO and provide a 2 orders of magnitude lower rate constant estimate for the OH channel. Hence, low-temperature generation of chain carriers has to be attributed to secondary reactions of HOCH(OO)CHO.

The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO₂ (ƒCO₂) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy (cw‐CRDS) for autonomous underway measurements of ƒCO₂ and the stable carbon isotope ratio of DIC [δ¹³C(DIC)] is explored. For the first time, by using a conventional air‐sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany—Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO₂ monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO₂ = 0.35 µatm for atmospheric and ΔƒCO₂ = 2.5 µatm and Δδ¹³C(DIC) = 0.33‰ for seawater measurements have been achieved. Whereas “calibration‐free” ƒCO₂ monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO₂, equilibrium δ¹³C(CO₂), δ¹³C(DIC), and pO₂ aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.

The kinetics of the allyl + O ₂ reaction has been studied in a flow tube reactor, using VUV synchrotron radiation for product detection.

Cavity ringdown spectroscopy (CRDS) in the linear absorption regime is a well-established method for sensitive trace gas detection, but only a few studies have addressed quantitative measurements in the presence of a saturated sample. In fact, saturation is usually avoided in order to escape from the required complex modeling of the saturation process that depends on the characteristics of the absorbing species, its interaction with the surrounding gas as well as on the temporal and spectral characteristics of the cavity excitation. Conversely, the novel saturated-absorption cavity ringdown spectroscopy approach (SCAR/Sat-CRDS) takes advantage of sample saturation in order to allow one to extract both the gas absorption and the empty cavity loss rates from a single ringdown event. Using a new continuous-wave infrared CRD spectrometer equipped with a tunable narrow-bandwidth high-power OPO laser system and a 18 bit digitizer, the transient dynamics of absorption saturation and the working limits of the Sat-CRDS approach in terms of its ability to extract reliable trace gas concentrations have been experimentally studied in this work. Using a strong methane transition as a test case, the excitation power P₀ and saturation power P_S have been systematically varied to explore a wide range of saturation regimes. At pressures 5 μbar < p < 2 mbar, the saturation intensity revealed a nearly linear pressure dependence showing that non-collisional processes contribute to the overall relaxation. A ratio of P₀/P_S ≈ 15 turned out to be optimal with working limits of 5 < P₀/P_S < 300. Moreover, the ratio of the absorption and empty cavity loss rates, γ_g/γ_c, has been varied to test the dynamic range of the method. At γ_g > γ_c, a pronounced coupling between the two parameters has been observed. Finally, a standard error analysis was performed revealing that the Sat-CRDS approach holds its advantages over conventional CRDS implementations in particular when the attainable ultimate detection sensitivity is limited by uncertainties in the empty cavity ringdown constant.