Recoil energy, kinetic

What are the relative roles of kinetic recoil energy and of electronic effects in leading to the observed products ... 

The average energy of the excited state will be Qn plus the kinetic energies of the particles, that is, the neutron plus the energy of the recoil. In this case the recoil energy is very small and could have been ignored. The recoil energy is obtained by conservation of momentum in the two-body decay. 

It should be also emphasized that the above calculations apply only to free tritium atoms, and not all of the recoil energy is available for the rupture of a chemical bond, since a fraction is expended as translational energy of the entire molecule (Carlson, 1960), as shown in the next Section. The distribution of the recoil energies of the daughter ions from the decay of free T atoms was calculated by Hsiung and Gordus (1965) as a function of the kinetic energy of the /8 particles. 

Finally, the molecule can be translationally, vibrationally, and rota-tionally excited by the distribution of the kinetic recoil energy of the daughter nucleus among the available degrees of freedom. It is apparent from these considerations that the general theoretical treatment of the molecular excitation and fragmentation caused by the /8 decay is quite difficult, even in the case of very simple molecules. Among several theoretical treatments, we will illustrate the time-dependent perturbation theory applied by Cantwell (1956) to the decay of molecular tritium. 

The kinetic energies that result from the Coulomb repulsion of these ions starting from the initial positions of the atoms in the molecule were calculated and found to be in qualitative agreement with the measured kinetic energy distributions, thus supporting the idea that most of the ionization occurs while the fragments are close to each other and the recoil energies result from the Coulomb repulsion of these ions. 

Use has been made of the relationship = P c (the photon rest mass is zero). Equation 3.34 gives the kinetic energy of the nucleus after the emission of a photon of energy E. This energy is called the recoil energy. 

No isolated lines are present in this spectrum, preventing a precise analysis of the lineshape. The linewidth of 5 GHz FWHM exceeds, however, substantially the spectral resolution and clearly indicates the fragment recoil. As shown in Fig. 3b, the lines may be approximated by a Gaussian profile so that the width of 5 GHz can be related to a most probable recoil speed v= 1430 m/s of C2(a II ) in a respective vibrational -rotational level, v corresponds to an average kinetic recoil energy of —2 CO2 photons of 10.591 pm, compared to 0.4 photons obtained in the previous experiment with the time-of-flight technique. 

If the /i-particle and the neutrino are emitted with the same momentum but in opposite direction, the daughter nucleus experiences no recoil. On the other hand, if they are both emitted in the same direction, or if all the energy is carried away with one of the particles, the daughter experiences maximum recoil. The daughter therefore recoils with kinetic energies from zero up to a maximum value (when the jS-particle is emitted with maximum energy). We can therefore write... 

The neutrino and antineutrino groups carry somewhat more than half of the decay energy, while the beta-particle group carries somewhat less than half. The kinetic energy of the product nuclide is very small because of the several-thousandfold smaller beta-particle mass. This recoil energy, in the range of a few electron volts, nevertheless may cause chemical change such as displacement of an atom from a crystal lattice. 

The recoil or kinetic energies of a number of species of interest are listed in Table 1. Other methods of producing atomic species with... 

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