Non-Born–Oppenheimer MCTDH calculations on the confined molecular ion

A multiconfiguration time-dependent Hartree method based on non-orthogonal coordinates has been developed. The method has been applied to the calculations of the properties of atomic and molecular systems beyond the Born–Oppenheimer approximation, treating electrons and nuclei on a similar footing. Example calculations have been performed on the confined H 2 + ion, treated as a genuine three-particle system. With only two orbitals per degree of freedom to begin with, the confinement energy levels as well as the origin of the genuinely bound H 2 + energy levels have been generated. The initial time evolution of the time-dependent orbitals is also shown.