Moderated Nuclear Recoil

In maintaining the narrow focus of this chapter, several important topics have been omitted. The caged recombination reactions that occur in condensed phase recoil experiments exhibit unusual dynamical characteristics (11,26,28,31,35,96). The energetic F-to-HF process shown in Equation 9 has been particularly important from a theoretical standpoint (22,24,29,30,32,34-37,39,40,43,44,49,52). The moderated nuclear recoil technique has provided accurate kinetic parameters for thermal F reactions (24,42,46,52-65,60) that have facilitated the recent development of a realistic potential extended collision theory for activationless bimolecular reactions (42,103),... 

Table II. Calculated Results for Tbermal Rate Constant Ratios Determined by the Moderated Nuclear Recoil Method in Model Systems...

The moderated nuclear recoil procedure for measuring thermal rate constants gives best results when the standard reaction against which the unknovm is measured has a rate constant smaller than the unknown, that is, 2/ 1 < I. This minimizes the importance of any hot contribution to the total yield from the unknown reaction. 

Limitations of the Moderated Nuclear Recoil Technique for Investigating Thermal Hydrogen Abstraction Reactions by Atomic Fluorine... 

Two component mixture calculations have been carried out via Eq. 13 for inert s moderated nuclear recoil F vs. 

Later sections describe the modeling procedure and results obtained for nuclear recoil atoms reacting with pure (70) and inert gas moderated (71) H2. These reaction systems have been chosen for study because of the availability of quasl-classical trajectory reaction cross sections (51) together with results from thermal (21.72) and nonthermal ( 7 nuclestr recoil experiments. 

The use of nuclear techniques allows the determination of C, N, H, O, and heavier contaminants relative fractions with great accuracy, and of the elements depth profile with moderate resolution (typically 10 nm). Rutherford backscattering spectroscopy (RBS) of light ions (like alpha particles) is used for the determination of carbon and heavier elements. Hydrogen contents are measured by forward scattering of protons by incident alpha particles (ERDA) elastic recoil detection analysis [44,47]. 

The major use of D20 is as a moderator for neutrons in nuclear reactors. Because the deuterium atom is small, neutrons colliding with it cause the deuterium atom to recoil so that more energy is absorbed than would be if the atom did not recoil. Thus, heavy water... 

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