### Session R1: Poster Session III

1:00 PM–1:00 PM, Wednesday, March 23, 2005

LACC Room: Exhibit Hall 1:00-4:00pm

Abstract ID: BAPS.2005.MAR.R1.53

### Abstract: R1.00053 : Highly compact wavefuntions for He-like systems

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#### Author:

Frank E. Harris

(University of Utah and University of Florida)

Wavefunctions which are compact, but still quite accurate, are extremely valuable as tools for gaining understanding of quantum systems. Here we study the ground electronic states of the three-body systems comprising the He isoelectronic series, using spatial wavefunctions that depend exponentially on all the interparticle distances, i.~e. built from a basis whose members are of the form $\phi_i=(1+{\sf P}_{12})\exp(-\alpha_i r_1 -\beta_i r_2 -\gamma_i r_{12})$, where $r_1$ and $r_2$ are the electron nuclear distances, $r_{12}$ is the electron-electron separation, and ${\sf P}_{12}$ permutes the electron coordinates. When the nonlinear parameters $\alpha_i$, $\beta_i$, $\gamma_i$ are carefully optimized (a nontrivial task), this type of basis is found to be extraordinarily efficient; using as few as four basis functions, it is found that nonrelativistic energies are reproduced to within 38 microhartrees of the exact values, an error far less than for compact wavefunctions previously proposed by others. Other properties, including those totally dependent upon the electron correlation, are also well represented.\\ Supported by U.S. National Science Foundation Grant PHY-0303412.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.MAR.R1.53