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Analytically projected rotationally symmetric explicitly correlated Gaussian Functions with one-axis-shifted centers

A new explicitly correlated functional form for expanding the wave function of an N-particle system with arbitrary angular momentum and parity is presented. We develop the projection-based approach, numerically exploited in our previous work [J. Chem. Phys. 149, 184105 (2018)], to explicitly correlated Gausssians with one-axis shifted centers and derive the matrix elements for the Hamiltonian and the angular momentum operators by analytically solving the integral projection operator. Variational few-body calculations without assuming the Born-Oppenheimer approximation are presented for several rotationally excited states of three- and four-particle systems. We show how the new formalism can be used as a unified framework for high-accuracy calculations of properties of small atoms and molecules.