Oxygen, paramagnetism

In this group, there are collisional interactions, which are responsible for quenching of excited states by molecular oxygen, paramagnetic species, heavy atoms, etc. [1, 2, 13-15]. Probability of such quenching can be calculated as ... 

The theoretical treatment of reaction (1), when catalyzed by paramagnetic centres, was developed by Wigner, 3>, and the reaction was shown to occur, using oxygen or nitric oxide in the gas phase, or oxygen, paramagnetic ions or free radicals in solution 14 1S>. 

It must be stressed that in many cases it is not easy to be certain of the reaction pathway, and traces of oxygen, paramagnetic impurities, or light may have a profound effect. The donor and acceptor characteristics of ligands are important in directing the course of the reaction. For example, while CpRh(CO)2 reacts... 

Effect of copper-oxygen paramagnetic complexes on nuclear magnetic relaxation... 

Oxygen paramagnetism is defined by the presence of a noncoupled electron pair on the antibonding molecular orbits. 

Oxygen is a colourless gas which condenses to a pale blue liquid, b.p. 90 K, which is markedly paramagnetic indicating the presence of unpaired electrons (p. 229). Simple valence bond theory (as used in this book) would indicate the structure... 

Mounting electrodes in a bioreactor is costly, and there is an additional contamination risk for sensitive cell cultures. Some other sensors of prac ticai importance are those for dissolved oxygen and for dissolved carbon dioxide. The analysis of gas exiting from a bioreactor with an infrared unit that detects carbon dioxide or a paramagnetic unit that detects oxygen (after carbon dioxide removal) has been replaced by mass spec trophotometry. Gas chromatographic procedures coupled with a mass spectrophotometer will detect 1 the volatile components. 

Other O2 Measurement Techniques The oxygen concentration in the emission gases of combustion processes is often measured based on the strong paramagnetic character of oxygen. A sampling line with appropriate sample treatments is required with this method. 

M. Faraday noted that oxygen was paramagnetic, correctly ascribed to the triplet ground state by R. S. Mulliken (in 1928). 

Oxygen condenses to a pale blue, mobile paramagnetic liquid (bp — 183.0°C at 1 atm). 

The product is a black-brown solid that is very sensitive to oxygen. The same cation can be obtained by oxidation of S4N4 with AsFs and is unusual in being the only sulfur-nitrogen (paramagnetic) radical that has been obtained as a stable crystalline salt. X-ray diffraction analysis shows the structure to be a planar 5-membered ring with approximate... 

The simplest of the ir-bondcd Re-C compounds is the green, paramagnetic, crystalline, therm ly unstable ReMen, w ich, after WMe, was only the second hexamethyl transition metal compound to be synthe zed 11976). It reacts with LiMe to give the unstable, pyrophoric, Lii[ReMe(,, which has a square-antiprismatic structure, and incorporation of oxygen into the coordination sphere greatly H reases the stability, wit e,ss Re CMe, which is thermally stable up to 200 C, and Re "0[Pg.1068]

This could account for the paramagnetism, but esr evidence shows that the 2 cobalt atoms are actually equivalent, and X-ray evidence shows the central Co-O-O-Co group to be planar with an 0-0 distance of l3l pm, which is very close to the 128 pm of the superoxide, 02, ion. A more satisfactory formulation therefore is that of 2 Co atoms joined by a superoxide bridge. Molecular orbital theory predicts that the unpaired electron is situated in a rr orbital extending over all 4 atoms. If this is the case, then the jr orbital is evidently concentrated very largely on the bridging oxygen atoms. 

Most oxygen trim systems interpose an additional link in the air/gas ratio controller. Others use an additional valve. Most types are based on the zirconia cell installed in the flue, while others use paramagnetic or electrolytic cell methods. The zirconia type has the advantage that there is no time lag in sampling, nor is there a risk of contamination of the sample. 

Elementary oxygen, like NO and NO is paramagnetic (Figure 7.3, p. 173). Experimental evidence suggests that the 02 molecule contains two unpaired electrons and a double bond. 

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