Using FM spectroscopy formyl radicals were detected for the first time behind shock waves. HCO radicals have been generated by 308 nm photolysis of mixtures of formaldehyde in argon. The HCO spectrum of the (A ˜2A 00 X ~2A 0 ) (09 0 0 00 1 0) transition was measured at room temperature with high resolution and the predissociative linewidths G of the individual rotational lines were fitted to G ¼ X + ZN 02 (N 0 + 1) 2 , where X ¼ 0.22 cm À1 and Z ¼ 1.0  10 À5 cm À1 . Since FM spectroscopy is very sensitive to small line shape variations the spin splitting in the Q-branch could be resolved.Time resolved measurements of HCO profiles at temperatures below 820 K provided the temperature independent rates of reaction ( 4), H + HCO ! H 2 + CO, and reaction (5), HCO + HCO ! CH 2 O + CO,and the low pressure room temperature absorption cross section of the Q( 9)P(2) line at 614.872 nm, a c ¼ (1.5 AE 0.4)  10 6 cm 2 mol À1 (base e).Measurements of the unimolecular decomposition of HCO, reaction (3) HCO + M ! H + CO + M, were performed at temperatures from 835 to 1230 K and at total densities from 3.3  10 À6 to 2.5  10 À5 mol cm À3 . They can be represented by the following Arrhenius expression. k 3 ¼ 4:0  10 13 ÁexpðÀ65 kJ mol À1 =RTÞ cm 3 mol À1 s À1 ðD log k 3 ¼ AE0:23ÞThe corresponding RRKM fit, 4.8  10 17 Á(T/K) À1.2 Áexp(À74.2 kJ mol À1 /RT ) cm 3 mol À1 s À1 (600 < T/ K < 2500), supports the lower range of previously reported high temperature rate expressions.

Despite the huge extent of the ocean's surface, until now relatively little attention has been paid to the sea surface microlayer (SML) as the ultimate interface where heat, momentum and mass exchange between the ocean and the atmosphere takes place. Via the SML, large-scale environmental changes in the ocean such as warming, acidification, deoxygenation, and eutrophication potentially influence cloud formation, precipitation, and the global radiation balance. Due to the deep connectivity between biological, chemical, and physical processes, studies of the SML may reveal multiple sensitivities to global and regional changes. Understanding the processes at the ocean's surface, in particular involving the SML as an important and determinant interface, could therefore provide an essential contribution to the reduction of uncertainties regarding ocean-climate feedbacks. This review identifies gaps in our current knowledge of the SML and highlights a need to develop a holistic and mechanistic understanding of the diverse biological, chemical, and physical processes occurring at the ocean-atmosphere interface. We advocate the development of strong interdisciplinary expertise and collaboration in order to bridge between ocean and atmospheric sciences. Although this will pose significant methodological challenges, such an initiative would represent a new role model for interdisciplinary research in Earth System sciences.

The rate of the reaction 1, HCO+O2-->HO2+CO, has been determined (i) at room temperature using a slow flow reactor setup (20 mbarH2+HCO+CO, into additional HCO radicals. The rate constants of reaction 4 were determined from unperturbed photolysis experiments to be k4(295 K)=(3.6+/-0.3)x10(10) cm3 mol-1 s-1 and k4(769-1107 K)=5.4x10(13)exp(-18 kJ mol-1/RT) cm3 mol-1 s-1(Delta log k4=+/-0.12).

The thermal decomposition of formaldehyde was investigated behind shock waves at temperatures between 1675 and 2080 K. Quantitative concentration time profiles of formaldehyde and formyl radicals were measured by means of sensitive 174 nm VUV absorption (CH 2 O) and 614 nm FM spectroscopy (HCO), respectively. The rate constant of the radical forming channel (1a), CH 2 O + M → HCO + H + M, of the unimolecular decomposition of formaldehyde in argon was measured at temperatures from 1675 to 2080 K at an average total pressure of 1.2 bar, k 1a = 5.0 × 10 15 exp(−308 kJ mol −1 /RT) cm 3 mol −1 s −1 . The pressure dependence, the rate of the competing molecular channel (1b), CH 2 O + M → H 2 + CO + M, and the branching fraction β = k 1a /(k 1a + k 1b ) was characterized by a two-channel RRKM/master equation analysis. With channel (1b) being the main channel at low pressures, the branching fraction was found to switch from channel (1b) to channel (1a) at moderate pressures of 1-50 bar. Taking advantage of the results of two preceding publications, a decomposition mechanism with six reactions is recommended, which was validated by measured formyl radical profiles and numerous literature experimental observations. The mechanism is capable of a reliable prediction of almost all formaldehyde pyrolysis literature data, including CH 2 O, CO, and H atom measurements at temperatures of 1200-3200 K, with mixtures of 7 ppm to 5% formaldehyde, and pressures up to 15 bar. Some evidence was found for a self-reaction of two CH 2 O molecules. At high initial CH 2 O mole fractions the reverse of reaction (6), CH 2 OH + HCO CH 2 O + CH 2 O becomes noticeable. The rate of the forward reaction was roughly measured to be k 6 = 1.5 × 10 13 cm 3 mol −1 s −1 .