Distribution recoil energy

Attempts have been made to calculate the recoil energy spectrum using an assumed statistical distribution of y-energies and direction. Notably, Hsiung et al. (39) have done this calculation for C1 produced by CCI4 (n,y). While the results of the calculation were in reasonble agreement with experimental data, the complexity of the necessary assumptions makes the agreement seem perhaps fortuitous. 

Such highly ionized species have been detected for Cl-37 produced by the EC decay of Ar-37 in gaseous phase ((>). In solids, however, such anomalous states are not realized or their life time is much shorter than the half-life of the Mossbauer level (Fe-57 98 ns and Sn-119 17-8 ns) because of fast electron transfer, and usually species in ordinary valence states (2+, 3+ for Fe-57 and 2+, 4+ for Sn-119) are observed in emission Mossbauer spectra (7,8). The distribution of Fe-57 and Sn-119 between the two valence states depends on the physical and chemical environments of the decaying atom in a very complicated way, and detection of the counterparts of the redox reaction is generally very difficult. The recoil energy associated with the EC decays of Co-57 and Sb-119 is estimated to be insufficient to induce displacement of the atom in solids. 

Similarly, for an absorbing particle initially at rest, when the photon is absorbed, the absorber will recoil. Then, the distributions of the emission and absorption energies are, consequently, separated by two times the recoil energy, 2ER (see Figure 1.42). In this case, the chance of resonant absorption is proportional to the overlap of both distributions. 

In order to obtain information about the energy distributions of reaction products, it is necessary to use a detection method that can determine either the internal state populations of the products or their recoil velocities. The methods employed to measure electronic, vibrational or rotational energy distributions are generally based on a form of emission or absorption spectroscopy, although there are other techniques that are sensitive to internal excitation. A variety of methods are used to measure recoil energy distributions these are commonly based on a mass spectrometric detection system used with some form of velocity analyser. 

For the reactions K + HBr and K + DBr, the KBr recoil energy distribution has been determined in a crossed-molecular beam experiment using a mechanical velocity selector. No difference was found in the form of the translational energy distributions for the two reactions for which a value of 0.30 may be derived. Although all the angular momentum appears in the product rotation, the moments of inertia for the alkali halides are large, which implies that the mean product rotational energy is quite small ( 0.21, 0.21 and 0.09 for K, Rb, Cs + HBr, respectively [3] these values are derived from the rotational temperatures obtained by electric deflection analysis). 

The reactions M + N02 have large reaction cross sections ( 100— 200 A2) and are consistent with a direct reaction proceeding by means of an electron jump. The MO product is scattered forward with low recoil energy [345, 346]. Visible chemiluminescence is observed from BaO (A Z) and this channel constitutes 0.18% of the total reaction [347]. The BaO (A) vibrational state distribution is found to be inverted with v = 8, 9 and 10 being preferentially populated. It is not expected that the NO fragment is appreciably excited. Polarisation measurements [344] of the BaO product in the chemiluminescent channel indicate a reasonable amount of the total angular momentum of the reactive collision appears as rotational angular momentum of the BaO product. 

---