Negative halogen ions

As the IE of a molecule is governed by the atom of lowest IE within that neutral (Chap. 2.2.2), the EA of a molecule is basically determined by the atom of highest electronegativity. This is why the presence of halogens, in particular F and Cl, and nitro groups make analytes become attractive candidates for EC (Table 7.3). [78] If EC occurs with a neutral of negative EA, the electron-molecule complex will have a short lifetime autodetachment), but in case of positive EA a negative molecular ion can persist. 

Collisions of some halogen bearing molecules, such as SF6, with Rydberg atoms result in attachment of the Rydberg electron to the molecule to form a negative molecular ion. Simple attachment, dissociative attachment, and attachment followed by autodetachment have all been observed. Collisions with attaching molecules are an excellent example of a process dominated by the electron... 

In these systems, the metal and oxygen or halogen ions are fourfold coordinated. ZnO and CuCl are the best examples of this group of solids. The tetrahedral coordination is usually associated with a substantial degree of covalency, and consequently the positive and negative centers do not carry the full charge (half of the value is considered a good approximation in many cases). 

Fluorine isHs 2p —Fluorine may be used to illustrate the main valence states of the halogens. The halogens may exist in three different valence states of which the monovalent, neutral atom /, the singly charged, negative, zerovalent ion II are well known in addition, however, there is a third possibility a singly charged, positive, divalent ion IIL... 

The more positive halogen of this polarized molecule is then abstracted by the alkene to form a carbonium ion, leaving a negative halide ion. This halide ion, or more probably another just like it, finally collides with the carbonium ion to yield the product, a dihalide. 

Vertical electron affinities /1V(XY) and adiabatic electron affinities / (XY) of the halogens and well depth D0(XY ) of their negative molecular ion ground states, all in eV. The uncertainties of all values are in the order of 01 eV, except Ay which has an uncertainty of +0-5 eV (Person, 1963 Baede, 1972 Auerbach et al., 1973)... 

The adiabatic electron affinities /lad(XY) of the halogen molecules XY, measured by the Amsterdam group, are shown in Table V together with the vertical electron affinities of Person (1963). In this table the well depths D0(XY-) of the negative molecular ions are also given, calculated from the relation... 

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