FOCKS EXPANSION, KATOS CUSP CONDITIONS, AND THE EXPONENTIAL ANSATZ

We have examined the recent solution of the Fock expansion through O(r2) for the ground state of the helium atom and have verified that it correctly treats the discontinuity in the local energy characteristic of the triple-collision point. We have also developed an exponential representation of the Fock expansion that satisfies Kato's cusp conditions for two-particle collisions even when the expansion is truncated at a finite order.