Reaction with atomic krypton

The kinetics of the reactions of chlorine atoms with a series of halogenomethanes have been investigated using mass-spectrometric techniques. The reactions of hot Br, produced by an (n, y) reaction with CHsBr, were studied in the presence of helium and krypton as moderators the results obtained were compared with those previously established for the formally analogous reaction between hot C1 and CH3CI. 

The Group 18 elements are called the noble gases because of their low reactivity. Like a noble man (as opposed to a nobleman) who does not interfere with others, these elements rarely involve themselves in reactions with other atoms. These gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). 

The d9 species (OC)2NiCHO has been prepared by the reaction of H atoms with Ni(CO)4 in a krypton matrix at 77 K. The complex is not thermally interconvertible with its isomer, HNi(CO)3, and EPR spectroscopy reveals that components in the xy plane of the principal g-values gzz = 2.0024(2) and gxx = gyy = 2.0207(2) split at 4K. Hence, structure (1004) was proposed. 411 The oxides KNa2[Ni02] and K3[Ni02] contain Ni1 with virtually linear coordination.24 2... 

Fig. 4.30. Angle-resolved transfer-ionization cross sections, reaction (4.35), relative to those at 0°, for positron-argon and positron-krypton collisions at impact energies of 75 eV, 90 eV and 120 eV (Falke et at, 1995, 1997). Reprinted from Journal of Physics B30, Falke et al., Differential Ps-formation and impact-ionization cross sections for positron scattering on Ar and Kr atoms, 3247-3256, copyright 1997, with permission from 10P Publishing.

The photolysis of pure methane in the solid phase and of methane in argon or krypton matrices has been examined by Ausloos et at 1236 A. The photolysis of solid methane is very similar to the gas-phase photolysis. Hydrogen and ethane are the major products, with CH4-CD4 mixtures showing an H2 and D2 richness over HD, and a predominance of d, d, d and rfg fractions in ethane. These features are indicative of molecular elimination of hydrogen followed by insertion of CH2 into methane. It was found that the smaller but significant contribution of ethane- s was greater than that of either ethane- i or d. This has been interpreted as evidence for the primary photolysis of methane into a hydrogen atom and a methyl radical. The fact that little ethane- i or is found excludes the formation of the methyl radicals by the dissociation of a hot ethane molecule after insertion by CH2. The minor products of photolysis are ethylene, propane, butanes, propene and pentanes. The presence of ethylene-[Pg.68]

Chemical Reactions. Products from gas-phase chemical reactions can also be trapped in rare gas matrices, and those products which absorb light can be studied by optical spectroscopic techniques. For example (31), the products from a low pressure 1 mm. of Hg) atomic flame of oxygen atoms plus acetylene were allowed to leak through a small oriflce in a borosilicate glass reaction chamber, where they were mixed with an excess of gaseous krypton at 1(H mm. of Hg pressure. The mixture was condensed on a quartz window cooled to liquid helium temperature. The only detectable small free radical found was HCO, but it was present in considerable quantities. Similar experiments by Harvey and Brown (23) showed that HNO could be easily produced and trapped from the gas-phase reaction of hydrogen atoms plus nitric oxide. 

In the same discharge-flow system no evidence was found for the reaction of F atoms with krypton in helium at 298 K, and an upper limit of 2 x 10 cm molecule s was set for the rate constant of the reaction... 

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