Carbon monoxide photodissociation

During interaction of hydrogen or carbon monoxide photoexcitation centres of Si02 surface containing ions of five valance vanadium one observes a surface-adjacent photodissociation of hydrogen and photooxidation of carbon dioxide through the following scheme [93, 96]... 

The darkness associated with dense interstellar clouds is caused by dust particles of size =0.1 microns, which are a common ingredient in interstellar and circum-stellar space, taking up perhaps 1% of the mass of interstellar clouds with a fractional number density of 10-12. These particles both scatter and absorb external visible and ultraviolet radiation from stars, protecting molecules in dense clouds from direct photodissociation via external starlight. They are rather less protective in the infrared, and are quite transparent in the microwave.6 The chemical nature of the dust particles is not easy to ascertain compared with the chemical nature of the interstellar gas broad spectral features in the infrared have been interpreted in terms of core-mantle particles, with the cores consisting of two populations, one of silicates and one of carbonaceous, possibly graphitic material. The mantles, which appear to be restricted to dense clouds, are probably a mixture of ices such as water, carbon monoxide, and methanol.7... 

J. A. Westrick, J. L. Goodman, K. S. Peters. A Time-Resolved Photoacoustic Calorimetry Study of the Dynamics of Enthalpy and Volume Changes Produced in the Photodissociation of Carbon Monoxide from Sperm Whale Carboxymyoglobin. Biochemistry 1987, 26, 8313-8318. 

Caldwell, K, Noe, L. J, Traylor, T. G. "Photodissociation of Carbon Monoxide Forms of Synthetic Heme Complexes Using Picosecond Absorption Spectroscopy", unpublished results, National ACS Meeting, Miami Beach, April 1985. 

Sakakura, M., Yamguchi, S., Horota, N., and Terazima, M. 2001. Dynamics of structure and energy of horse carboxymyoglobin after photodissociation of carbon monoxide. 

Teng, T. Y., Srajer, V., and Moffat, K. 1997. Initial trajectory of carbon monoxide after photodissociation from myoglobin at cryogenic temperatures. Biochemistry 36 12087-12100. 

The studies of Hasinoff [53] on the recombination rate of carbon monoxide and the heme units after photodissociation of carboxy ferrous microperioxidase come close to satisfying the requirements for observing the effects of anisotropic reactivity and rotational diffusion on the rate of a translational diffusion-limited reaction. In Chap. 2, Sect. 5.6, the details of this study were briefly mentioned. Hasinoff found that the rate of recombination was substantially diffusion-limited in all three aqueous solvents used at 260 K, but at higher temperatures, the rate of reaction of the encounter pair, feact, was a significant factor in determining the overall rate of recombination (see Fig. 9). The observed rate coefficient of recombination, feobs, was separated into the rate coefficient of diffusive formation of encounter pairs, feD, and the rate coefficient of reaction of encounter pairs, fcact, with the Collins and Kimball expression, eqn. (26)... 

Decomposition of carbon monoxide takes place when it is exposed to radiation of wavelength 1,295 A, but not when exposed to 1,470 A -0. Herzberg2i5 has concluded from this that Z)(CO)<9-57 eV, but Gaydont< 6 has pointed out that when vibrational and rotational energy are taken into account the upper limit may be as high as 10 1 eV, and further that it is not established that photodissociation is the primary act in the reaction. 

Time-Resolved Resonance Raman Study of the Recombination Dynamics Photodissociated Carbon Monoxide to Sperm Whale Myoglobin and Its Mutants... 

In almost all of the gas-phase kinetic-mechanistic studies on sulfur atom reactions made to date, the source has been the in situ photolysis of carbonyl sulfide (COS). The reasons for this choice are not far to seek. Carbonyl sulfide is a stable, readily available gas. Its absorption spectrum is located in a convenient spectral region and the carbon monoxide formed in the photodissociation provides an excellent internal monitor for sulfur atom production. 

The observation of the photodissociation of phosgene into carbon monoxide and dichlorine at room temperature soon followed [398]. 

Photolysis of dimethylketene, which underwent thermal dimerization into tetramethyl-cyclobutane-1,3-dione, gave tetramethylcyclopropanone 1, together with 2,3-dimethylbut-2-ene (from dimethylcarbene dimerization) and carbon monoxide (from ketene photodissociation). Formation of the three-membered ring most probably arises from the addition of dimethylcarbene to dimethylketene. ... 

In a typical experiment, the photodissociation of the carboxyhemochrome leads to the formation of carbon monoxide and the five-coordinate iron(II), then O2 and CO compete for rebinding. If we choose adequate ligand... 

Thus the net effect of dissociating nitrogen dioxide is neutral. Net production of tropospheric ozone occurs as a result of other reactions that convert NO into NO2 without destroying ozone. There are many such reactions, most of which involve the photooxidation of chemicals like carbon monoxide, methane and other hydrocarbons. Since these are produced by traffic and industrial processes, ozone production is a feature of polluted regions, and ozone itself is considered a pollutant at low levels of the atmosphere where it is detrimental to human and other life forms. Sinks of ozone include photodissociation and reactions with OH and HO2 (as in the stratosphere) and deposition. 

It is important to note that certain cycles can lead to ozone formation this phenomenon is readily observed in the troposphere (see Box 5.4), which is rich in anthropogenic hydrocarbons and nitrogen oxides. In the free troposphere and lower stratosphere, the conversion of NO to NO2 by peroxy radicals (HO2 and CH3O2) produced by the oxidation of methane and carbon monoxide, followed by the photodissociation of NO2 leads to the formation of O3. The complete chains are the following (Crutzen, 1974) ... 

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