Hot atom

Shalashilin D V, Jackson B and Persson M 1999 Eley-Rideal and hot atom reactions of H(D) atoms with D(H)-covered Cu(111) surfaces quasiclassical studies J. Chem. Phys. 110 11 038... 

Hot atom reactions have also been used to label organic compounds with T. Irradiation of helium-3 with neutrons according to the nuclear reaction produces very energetic tritium atoms that can displace ordinary hydrogen in organic compounds. This procedure is not very selective, and the labeling pattern must be determined to enable the tritiated product to be used effectively as a tracer (34). 

The next stage, which we ought to try to reach as soon as possible, is that of measurement of physical parameters of the systems so as to relate hot atom chemistry to other areas of physical chemistry. Here one would think immediately of the possible use of electron spin resonance to observe the existence and stability of the various radical species which have been postulated or inferred to occur in several systems -Cr(CO)j., Mn(CO)5, -FeCp, As 2> others. One might... 

Recent work (51) on FeCpj irradiated in Fe(CO)5 solutions (to give FeCpj) has shown that the Fe atom can come from the Fe(CO)j molecule. The mechanism is unknown and may well involve exchange or other reactions in solution in addition to hot atom reactions. The results do show, however, that it is not necessary to preserve the Fe-Cp bonding in order to reform FeCpj. In frozen solutions the yield of FeCpj is much lower than in liquid solutions. 

The only respect in which the hot atom chemistry of organometallic compounds has so far been applied to other fields of study is in the area of isotope enrichment. Much of this has been done for isolation of radioactive nuclides from other radioactive species for the purpose of nuclear chemical study, or for the preparation of high specific activity radioactive tracers. Some examples of these applications have been given in Table II. The most serious difficulty with preparation of carrier-free tracers by this method is that of radiolysis of the target compound, which can be severe under conditions suited to commercial isotope production, so that the radiolysis products dilute the enriched isotopes. A balance can be struck in some cases, however, between high yield and high specific activity (19, 7J),... 

Sano, H., Giitlich, P. Hot Atom Chemistry. Kodansha, Tokyo (1984) (and references therein)... 

Figure 4.21 Evidence for the hot atom concept from ionisation laser spectroscopy.

The light contains energy, so Equation (9.1) alerts us to the truth that the body M has acquired energy during the photochemical reaction. We sometimes say that the product is a hot atom, ion, etc. for this reason. This energy cannot just be tacked on to the body M, but is stored within it in some way, so the asterisk against the product shows that it is formed in an excited state. 

So, in summary, photo-initiated chlorination of methane requires UV light to generate hot atoms of molecular chlorine, which subsequently dissociate ... 

Contents Introduction. - Experimental Techniques Production of Energetic Atoms. Radiochemical Separation Techniques. Special Physical Techniques. - Characteristics of Hot Atom Reactions Gas Phase Hot Atom Reactions. Liquid Phase Hot Atom Reactions. Solid Phase Hot Atom Reactions. - Applications of Hot Atom Chemistry and Related Topics Applications in Inorganic, Analytical and Geochemistry. Applications in Physical Chemistry. Applications in Biochemistry and Nuclear Medicine. Hot Atom Chemistry in Energy-Related Research. Current Topics Related to Hot Atom Chemistry and Future Scope. - Subject Index. 

It should be unaffected by the presence of Cl2 and Br2, which could not compete effectively with these reactions at the halogen HC1 ratios shown in Fig. 5(a) and (b). Thus hot atom reactions can account for the residual (or unscavengeable) hydrogen, GH = 2.2, as well as contribute to the yield of scavengeable hydrogen atoms. 

Atomic Eorce Microscopy Studies of Transition Metal Chalcogenide Deposition Using Translationally Hot Atoms (from Spain, 1997)... 

Because of the large W, a 1 for reactive atoms. However, the dynamics within the well before thermalization is anything but simple. Because of the strong corrugation, there is considerable scrambling of En and E. When /jl is very small (H and D), energy dissipation to the lattice in the well is slow and hot atoms are formed which have considerable reactivity with other species adsorbed on the surface(see Section 4.1.2). 

In addition to the fully LH reaction of + CO, C02 apparently produced by hot atoms is also observed by thermal dissociation [367], photochemical dissociation [368,369] or collisional dissociation [370] of 02 co-adsorbed with CO. Dosing a CO adsorbed layer with gas phase atoms also appears to give the same hot atom reaction, i.e., reaction prior to the atom fully equilibrating with the surface [371]. In all cases, the oxidation occurs at Ts far below the thermal LH... 

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