Born–Oppenheimer potentials for Π, Δ, and Φ states of the hydrogen molecule

We report on accurate variational calculations of the Born–Oppenheimer potential for excited states of the hydrogen molecule with Π,Δ, and Φ symmetries. The obtained potential energy curves reach the relative precision of 10−9 or better along internuclear distances of 0.01–20 au. Calculations rely on the recursive evaluation of two-centre two-electron molecular integrals with exponential functions in arbitrary precision arithmetics. Our results for most of the states are the first-ever reported, and for the previously calculated states constitute an improvement by several orders of magnitude.