Accurate electron number densities and interelectronic distance (intracule) densities are given in simple algebraic form for the ground states of H-, He, Li', Be2+, B3+, and Ne". The densities are obtained from systematic sequences of increasingly accurate Hylleraas-type wave functions. The most accurate densities are obtained from 204-term wave functions that lead to variational energies no more than 16 nano-Hartrees above the exact ones. The algebraic densities permit the evaluation of systematic sequences of many expectation values. Some moments of the densities are evaluated in this manner. 0 1993 John
An (e,2e) apparatus for electron momentum spectroscopy (EMS) has been developed, which employs an ultrashort-pulsed incident electron beam with a repetition rate of 5 kHz and a pulse duration in the order of a picosecond. Its instrumental design and technical details are reported, involving demonstration of a new method for finding time-zero. Furthermore, EMS data for the neutral Ne atom in the ground state measured by using the pulsed electron beam are presented to illustrate the potential abilities of the apparatus for ultrafast molecular dynamics, such as by combining EMS with the pump-and-probe technique.
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