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 gase ous phase, (k(a))(th), and thermal electron attachment rate constants for a number of molecules in liquid cyclohexane, (k(a))(L), are summar ized in an effort to discern the dependence of the thermal electron at tachment rate constant for molecules embedded in gases and in liquids on the energy position, E(NIS), of the electron attaching state. For t hese molecules the (k(a))(th) varies only slightly with E(NIS), as lon g 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 exc ept that it remains virtually constant well above 0.0 eV, up to E(NIS) approximate to 0.9 eV. and thereafter decreases precipitously. This e nergy shift between the gaseous and the liquid phase correlations is c onsistent with the magnitude of the polarization energy of the anions in liquid cyclohexane and its effect on E(NIS). It indicates that in t he liquid phase the rate constant (k(a))(L) for these molecules is ess entially 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 concl usion may be of wider validity.