Mead can be explained in terms of barrier distortion due to negative space charge within the insulator arising due to the occupation by electrons of deep traps therein.

When monoenergetic atoms are continuously introduced into a thermal gas, they can undergo deactivating, activating, and reactive collisions. The net result of such collisions is to establish a steady-state distribution of laboratory energies which, although not as sharp as the initial distribution, preserves some of its features, such as being centred at about the initial energy. The reactive collisions which occur under these conditions are characterized by the associated relative energy distribution function and the energy-dependent reaction cross section. As a result, as the initial laboratory energy of the atoms is experimentally varied, the relative energy distribution function can be made to sample appropriately the reaction cross section curve. Therefore, from measurements of the competition between reaction and thermalization processes as a function of initial atom laboratory energies, and from a knowledge of the non-reactive differential scattering cross section, it is possible to obtain information about the dependence on relative energy of the rotationally averaged reaction cross section. The appropriate Boltzmann steady-state equation needed to obtain this information is derived in this paper and solved for an assumed set of reactive and non-reactive cross sections. Distribution functions of relative energies are thereby obtained and used to indicate the usefulness of the suggested measurements. STEADY-STATE B O L T Z M A N N EQUATIONSWe consider atoms A of mass m, continuously introduced into a thermal gas of molecules B of mass nz2 which is at temperature T. Let Ro be the total rate of generation of atonis A and let qo(vl) be the normalized distribution describing the laboratory velocity vectors v, with which A is introduced into the gas ; +o(vl) will be considered spherically symmetrical but otherwise arbitrary. For the case of interest in the present paper it will be a rather narrow distribution function centred around an initialspeed d ? ) . Inparticular it can be a 6 function at d?). The rate of introduction Ri(v,)dvl of atoms A in velocity range v1 to v1 +dv, is therefore Ro+o(vl)dvl. Under steady-state conditions, let g(vl)dv, be the concentration of D atoms in that same velocity range. The rate R(-) (v,)dv, at which atoms are removed from that range due to reactive and non-reactive collisions is given by where * work supported in part by the U.S. Atomic Energy Commission. Report Code : CALT-532-13. t contribution no 3537. 46

A recently suggested method for constructing ah initio pseudopotentials has been applied to Li and used to calculate the energies at high-symmetry points of the Brillouin zone for lithium metal. This potential is unique, local, and Hermitian and is much weaker than the Hartree-Fock potential. As a result of the weakness of the potential, the conduction-band orbitals are smooth in the core regions, and plane-wave expansions are found to converge rapidly. (There is no restriction that the conduction orbitals be made orthogonal to the core orbitals.) The lowest energy band has character similar to the band obtained from orthogonalized planes-wave calculations using the Seitz empirical potential.

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