Elastic electron scattering amplitudes for neutral atoms were calculated using the partial wave expansion method for 10-, 40-, 70-, and 100-kV incident electrons. The partial wave phase shifts were calculated by numerical intergration using the phase amplitude method until the results converged to values obtained using the WKBJ and first Born approxmations, which were then used in the remainder of the partial wave sum. The static potential field of the target atoms was represented by an analytical expression involving a sum of Yukawa terms. Potential field parameters for the expression were obtained by a least-squares fit of the radial electron distribution function, D (r), using Hartree—Fock and relativistic wavefunctions for all the neutral atoms from Z=1 to Z=54. For the smaller atoms from Z=1 to Z=21, Clementi Hartree—Fock wavefunctions were used and for the atoms from Z=22 to 54 Liberman—Waber—Cromer D (r) curves calculated using the Dirac Hamiltonian incorporating a j—j coupling scheme and the Slater ⅔ approximation in the exchange potential were used.

Approximate analytical expressions for the electrostatic potentials of neutral Thomas—Fermi—Dirac atoms have been obtained by fitting a sum of three exponential terms to the tabulated values by least-squares methods. The six different parameters used for each atom are expressed as functions of the atomic number. The corresponding expressions for the radical electron density, the mean-square radius, the diamagnetic susceptibility, the atomic scattering factors for x rays and the atomic scattering factors for electrons according to the first Born approximation are given. The accuracy of the approximate expressions are discussed in relation to results obtained from the tabulated values of the electrostatic potential and from the corresponding electron density.

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We report the implementation of covariance mapping mass spectmscopy to pulsedelectrowbeam ionization time-of-flight mass spectroscopy. The technique has been applied .~..

A number of correlated wavefunctions of simple form were investigated for heliumlike atoms. Instead of the usual Hylleraas expansion the wavefunctions considered contained exponential correlation functions with nonlinear variational parameters. Wavefunctions of this type are usually avoided because of the nonlinear parameters. However, this type of function was chosen to try to determine some simple but relatively good wavefunctions for use in computing atomic properties. Results for atomic numbers 1 through 3 are presented.