Laboratory threshold energy

This particular reaction is of interest for several reasons. It was the first nuclear reaction that was produced in a laboratory by means of artificially accelerated particles (Cockcroft and Walton 1932 cf. 13.3). Reaction (b) is still used for the production of y-radiation (17 MeV), while reaction (c) is used as a source of mono-energetic neutrons. The energy of the neutrons from reaction (c) is a function of the proton energy and the angle betwe the neutron and the incident proton beam. A necessary requirement, however, is that the threshold energy (1.64 X (8/7) = 1.88 MeV) must be exceeded, the g-value for reaction (c) being —1.64 MeV. 

One of the first examples from our laboratory [13] which suggested that photodissociation thresholds could yield quantitative metal-ligand bond energies was from a comparison of the photodissociation spectra of FeOH+ and FeC0+ obtained by monitoring reactions 9 and 10, respectively, and shown in Figure 3 The two spectra are remarkably similar with two absorption maxima observed... 

The reported laboratory distributions differ. The more recent measurements of Geddes, Krause, and Fite indicate that DH is scattered mainly into the backward hemisphere. Excited vibrational levels of HD are not energetically accessible in the majority of reactive encounters, which will occur at energies fairly close to threshold [ 0 = 7.6 kcal/mole (0.33 eV) (17)], and consequently the energy must be released mainly in relative translation of the products, generating H atoms which are quite hot [90]. 

Fig. 4. Multi-collision CID results for (C2H2)3Fe+ and (C6H6)Fe+ in the laboratory energy scale with He as the collision gas. (C2H2)3Fe+ is produced by sequential addition of C2H2 to Fe+ and (C6H6)Fe+ is produced by direct addition of C6H6 to Fe+. The similarity in the threshold for dissociation of (C2H2)3Fe+ and (C6H6)Fe+ suggests that Fe+ has mediated the cyclotrimerization of acetylene to benzene [35]...

Fig. 4. Total cross section for the CID of Cr(CO)6+ with Xe, extrapolated to zero pressure, as a function of collision energy in the center-of-mass frame (lower x-axis) and laboratory frame (upper x-axis). The solid line shows a representative fit to the data using the model of Eq. (4) convoluted over the energy distributions of the two reactants. The dashed line shows the same model in the absence of energy convolution, for reactants with an internal temperature of 0 K. A 50x magnification of the threshold region of the cross section is presented in the upper left side of the figure. Adapted from [9]...

The interface which runs these codes carries out extensive checks on input so that a user cannot attempt to carry out calculations for non-existent orbitals, or energies below the threshold for a transition. It is hoped that similar methods of allowing users to access codes at other institutions will be developed. Preliminary work is now being carried out at the Los Alamos National Laboratory to determine the feasibility of making some of the atomic physics codes from that institution available to outside users. If this effort is successful it is hoped that similar efforts can be initiated at other institutions so that in the future it will be possible to generate data for a wide range of processes of interest to fusion energy research. 

Interest in DIBT studies at oxides surfaces underwent an explosion in 1978, when Knotek and Beibelman at Sandia Laboratories [84] reported a new mechanism for BSD, the so-called "Auger decay of a core hole". The model explained well the thresholds and ion kinetic energy distributions for the ejection of O, ... 

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