Formaldehyde photodissociation, production

Reactions with molecular species above the arrow e.g. RIO) involve subsequent reactions with these species to produce the indicated products. In most cases the reactants shown to the left of the arrow participate in the slowest or rate-determining step]. The CH3O radical formed in Rll then follows reaction R7. The H02 radical formed in RIO is the other member of the family and is linked with HO in a variety of chain reactions. These radicals are produced following HO attack on hydrocarbons or by photodissociation of oxygenated hydrocarbons such as formaldehyde (RIO) and acetaldehyde ... 

The photolysis of methyl nitrite at low temperature in an argon matrix was studied157. The products include formaldehyde, and nitroxyl HNO which also reacts to form N2O and water. The 355-nm photodissociation of gaseous methyl nitrite has been studied by monitoring the nascent NO product using a two-photon laser-induced fluorescence... 

Butenhoff, T.J., Carleton, K.L., and Moore, C.B. (1990). Photodissociation dynamics of formaldehyde H2 rotational distributions and product quantum state correlations, J. Chem. Phys. 92, 377-393. 

Molecular hydrogen is assumed to be well mixed in the troposphere, with a mixing ratio of 0.4 to 0.6 ppm [Junge (128) and Scholz, Ehhalt, Heidt, and Martell (219)]. Koyama (142) found that swamps and paddies are very small natural sources. Levy (153) proposed both an atmospheric source (photodissociation of formaldehyde) and an atmospheric sink (oxidation by hydroxyl radical). From daily average number densities for the hydroxyl radical and a daily average hydrogen production rate,... 

Townsend et al. were able to further resolve the photodissociation of formaldehyde to show that the rotationally highly excited CO was accompanied by vibrationally cold H2, as expected for a reaction over a single-concerted TS (shown in Figure 8.21 as 95). A smaller component, observed at higher photon energies, involves production of rotationally cold CO and vibrationally hot H2. A PES created by fitting energies, computed at CCSD(T)/aug-cc-pVTZ, for... 

In order to estimate the rate of hydrogen production from the oxidation of methane by OH radicals it is convenient to assume that photodissociation is the dominant loss process for formaldehyde. From the photodissociation coefficients (see Fig. 2-19), one finds that the channel leading to H2 + CO as dissociation products contributes roughly 68% to the overall photodecomposition process. The rate of H2 formation thus is... 

Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photochemical smog ... 

Formaldehyde, as noted earlier, is subject to photolysis, and it reacts with OH as well. Two channels exist for photodissociation. One leads to CO and H2 as stable products, the other channel produces a formyl radical, which reacts further with oxygen to produce CO and an HO2 radical... 

Basic questions are analyzed, as is the case for the photochemistry of formaldehyde. Contrary to previous results, direct quantum dynamics simulations showed that the H2 + CO H + HCO branching ratio in the Si/Sq nonadiabatic photodissociation of formaldehyde is controlled by the direction and size of the mean momentum of the wavepacket when it crosses the seam of conical intersection. In practice, if the wavepacket falls down from the barrier to the conical intersection with no initial momentum the system leads to H2 + CO, while an extra momentum toward products favors... 

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