Govecnm_t retmns rovalty-_ _ to _ nonexclum_, or ral_oduce ' the pubiist_ fom_ of this _, alk)w others to do so, for U.S. I. j' autodetachment aad , ionization ai, and the associated physical quantities [e.g., the electron affinity EA, the vertical attachment energy VAE, the vertical detachment energy VDE, the ionization threshold energy I, and the polalization energy of the positive (PW) and the negative (P-)ions] are all strong functions of the nature and density of the medium in which these elementary physical processes occur. While these physical quantities have well-defined values at low-gas number densities, they ' assume a spectrum of values in dense media.. Understanding these effects is a prerequisite for the successful use of physicochemical knowledge in establishing mechanisms of radiobiological action and in developing novel radiobiological instrumentation. This article is on basic radiation interaction processes in dense fluids and on interphase studies aiming at the interfacing of knowledge on radiation interaction processes in the gaseous and the liquid state of matter. It is specifically focused on the effect of the density and nature of the medium on electron production in irradiated fluids and on the state, energy, transport, and attachment of slow excess electrons in dense fluids especially dielectric liquids which possess excess-electron conduction bands (V o < 0 eV) [1-4]. Studies over the past twodecades have shown that the interactions of low-energy electrons with molecules embedded in dense media depend not oItly on the molecules themselves [1-7] and their internal state of excitation [8-10], but also on the electron state and energy in =-and the nature and density of-the medium in which the interactions occur [3,4,11,12]. II. ELECTRON PRODUCTION IN DENSE FLUIDS A. Total and Free Electron Yields The processes by which isolated atoms and molecules are ionized by radiation, and the corresponding cross sections, have been well studied and are reasonably weil understood [1,2,5-7]. Measurements of electron impact ionization cross sections _7i(_) in gases are, for example, abundant. This, however, can not be said of dense fluids. In these, there exist measurements of only the density, N, normalized ionization "" ' ' a/x,_ coelI_Cl_nl, &g _1, IUlI.L, blU_.I Ul.
