The dependence of the thermal electron attachment rate constant in gases and liquids on the energy position of the electron attaching state

Thermal electron attachment rate constants for halocarbons in the gaseous phase, (k(a))(th), and thermal electron attachment rate constants for a number of molecules in liquid cyclohexane, (k(a))(L), are summarized in an effort to discern the dependence of the thermal electron attachment rate constant for molecules embedded in gases and in liquids on the energy position, E(NIS), of the electron attaching state. For these molecules the (k(a))(th) varies only slightly with E(NIS), as long as E(NIS) is < 0.0 eV (i.e., as long as the electron affinity of the molecule is positive), but it decreases precipitously with increasing E(NIS), when E(NIS) > 0.0 eV (i.e., when the electron affinity of the molecule becomes negative). The (k,), exhibits a similar behavior except that it remains virtually constant well above 0.0 eV, up to E(NIS) approximate to 0.9 eV. and thereafter decreases precipitously. This energy shift between the gaseous and the liquid phase correlations is consistent with the magnitude of the polarization energy of the anions in liquid cyclohexane and its effect on E(NIS). It indicates that in the liquid phase the rate constant (k(a))(L) for these molecules is essentially constant (and very large; often equal to diffusion-controlled values) as long as the energy E(NIS) of the electron attaching state in the liquid is < 0 eV, that is, as long as the molecule has negative ion state(s) which are lowered below 0.0 eV in the liquid. This conclusion may be of wider validity.