High-energy Reactions

Mass spectrometry is another valuable method for the investigation of high-energy nuclear reactions, in particular if an on-line arrangement is used in such a way that the reaction products are immediately transported from the target into the mass spectrometer or mass separator. The transport may be combined with a chemical separation in the gas phase. 

Some radionuclides produced in high-energy reactions exhibit characteristic properties and can be detected without chemical separation. Examples are Li, C, which emit delayed neutrons, or Be, B, C, Al, P, which 

Examples of monitor reactions that are applied for determination of cross sections with protons are (p, pn) C and Al(p, 3pn) Na. Cross sections for these reactions in the energy range between 50 MeV and 30 GeV are listed in Table 8.3. and A1 monitors are used in the form of plastic or A1 foils, respectively. 

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Raisen et al, Survey of the Thermochemistry of High Energy Reactions , AF Avionics Laboratories, Wright Patterson AFB, ASD-TDR-63-846 (1963) 9) A.F. Belyaev R.Kh. Kurbanga-... 

TSA (Transition state analogue) Frequently a stable analogue of an unstable, high-energy reaction intermediate that is close to related energy barriers in a multi-step reaction. 

TABLE 2.6 Typical AH Values for "High-Energy" Reactions... 

The heat released by the occurrence of the high-energy reaction raises the temperature of the next layer of composition. 

Reaction velocity is primarily determined by the selection of the oxidizer and fuel. The rate-determining step in many high-energy reactions appears to be an endothermic process, with decomposition of the oxidizer frequently the key step. The higher the decomposition temperature of the oxidizer, and the more endothermic the decomposition, the slower the burning rate will be (with all other factors held constant). 

Surface area of the reactants For a high-energy reaction to rapidly proceed, the oxidizer must be in intimate contact with the fuel. Decreasing particle size will increase this contact, as will increasing the available surface area of the particles. A smooth sphere will possess the minimum surface area for a given mass of material. An uneven, porous particle will exhibit much more free surface, and consequently will be a much more reactive material. Particle... 

In the Trauzl test, the mixture produced an expansion of 24 cc./gram, which is indicative of a high energy reaction. Card gap tests were also positive the value at room temperature is approximately 25 cards. From these results it was concluded that a mixture of methylene chloride with nitrogen tetroxide constitutes a definite explosive hazard. This conclusion was not immediately apparent as a result of compatibility and impact testing alone. Methylene chloride was not recommended as a solvent for cleaning N2O4 systems instead, a water flush is used for this operation. 

Li, Be, and B are believed to be produced in spallation reactions in which the interstellar 12C and 160 interact with protons in the galactic cosmic rays (GCR). These reactions are high-energy reactions with thresholds of 10-20 MeV. The energy spectrum of the GCR is shown in Figure 12.20. 

Hydrogen replacement with benzene and the halobenzenes has been studied. The isomer distribution has been found to be very close to the statistical one and interpreted as the result of high-energy reactions. Halogen replacement yields increase in the series F-, C1-, Br- and iodobenzene showing dependence on the C—X bond energy both in liquid and in gas phase. 

X A + B — 60 Kcal, orX— C-f-D —50 Kcal. (a) Show that the existence of the low-energy path, reaction 2, makes the high-energy reaction 1 less likely to happen. (6) By using the RRK model, derive a general expression for the rates of the two reactions. 

E. Henly, E. Johnson, The Chemistry and Physics of High Energy Reactions, University Press, Washington, DC, 1969... 

Recent advances in carbene chemistry demonstrate that constrictive hosts, like CyDs and FAUs zeolites are able to modify the selectivity of the high-energy reaction intermediate.42... 

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