Accurate long-range coefficients for two excited like isotope He atoms: He (2 P1) -He (2 P1), He (2 P1) -He (2 P3), and He (2 P3) -He (2 P3)

A general formalism is used to express the long-range potential energies in inverse powers of the separation distance between two like atomic or molecular systems with P symmetries. The long-range molecular interaction coefficients are calculated for the molecular symmetries ?, ?, and ?, arising from the following interactions: He (2 P1) -He (2 P1), He (2 P1) -He (2 P3), and He (2 P3) -He (2 P3). The electric quadrupole-quadrupole term C5, the van der Waals (dispersion) term C6, and higher-order terms C8 and C10 are calculated ab initio using accurate variational wave functions in Hylleraas coordinates with finite nuclear mass effects. A comparison is made with previously published results where available. � 2007 The American Physical Society.