Electron attachment to the fluoro, bromo, and iodomethanes studied by means of electron transmission spectroscopy and Xα calculations Electron attachment by chloro and bromomethanesThe relationship between thermal electron attachment and electron beam studies for chlorobenzene, o-dichlorobenzene, o-chlorotoluene, 3'-and 4'-chloroacetophenone, l-chloronaphthalene, bromobenzene, o-bromotoluene, 1-bromonaphthalene, and iodobenzene is shown. The empirical negative-ion potentialenergy function used to describe electron attachment to aliphatic halides is used for convenience in showing this relationship. Use of the two-dimensional potential-energy function permits a more quantitative representation of the mechanisms previously proposed. In some cases, the mechanisms have been altered from the earlier qualitative interpretation. In general the two types of measurement appear to be essentially in complete agreement. The agreement between the results further supports the empirical potential-energy function for the negative ion. Also, thermal electron attachment to additional aromatic halogen derivatives was investigated by the pulse sampling technique as a function of temperature to further support the mechanism. In particular, the thermal electron attachment of 3'-and 4'-chloroacetophenone shows a unique temperature dependence involving three different phenomena over the temperature range 30°-240°C, which adds further support to the proposed mechanisms. In all the other cases investigated (chlorobenzene, o-chlorotoluene, o-bromotoluene), the electron attachment shows only one temperature region, again in complete agreement with the proposed mechanisms.

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Articles you may be interested in Energies and relative cross sections of singlet-triplet transitions in methylsubstituted 1,3butadienes by ionimpact spectroscopyThe failure of previous calculations to predict the correct "forward-peaking" angular dependence of the electron-impact differential cross section for the helium 1'S->2 3 S transition is shown to be due to the neglect of the core contribution. Even a simple approximation to the jull Born-Oppenheimer transition amplitude based on an expansion in inverse powers of the incident electron momentum predicts the correct angular dependence of this transition for electron energies to within 40 eV of threshold. For electron-impact excitation of the lowest singlet->triplet transition in molecular hydrogen, the peaking of the differential cross section away from zero scattering angle is due mainly to a molecular diffraction effect, and the success of Ochkur's approximation in predicting this dependence is shown to be merely a consequence of the relatively small contribution made by the core terms for this particular transition and cannot be generalized. For higher singlet->triplet transitions in H2, the angular dependence of the differential cross section and the magnitude of the core contribution are shown to depend importantly on the separated atom state with which the molecular wavefunction correlates at infinite separation.

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