Accurate non-Born-Oppenheimer calculations of the complete pure vibrational spectrum of D₂ with including relativistic corrections

In this work we report very accurate variational calculations of the complete pure vibrational spectrum of the D₂ molecule performed within the framework where the Born-Oppenheimer (BO) approximation is not assumed. After the elimination of the center-of-mass motion, D₂ becomes a three-particle problem in this framework. As the considered states correspond to the zero total angular momentum, their wave functions are expanded in terms of all-particle, one-center, spherically symmetric explicitly correlated Gaussian functions multiplied by even non-negative powers of the internuclear distance. The nonrelativistic energies of the states obtained in the non-BO calculations are corrected for the relativistic effects of the order of ² (where 1c is the fine structure constant) calculated as expectation values of the operators representing these effects.