Two energetically equivalent Out configurations and the higher energy In configuration are identified by their configuration number n = 1, 2, and 3. The two deuterium atoms are labelled 2 and 3. Furthermore, is the equilibrium value of the torsional angle . Configuration 3, displaying a symmetry plane and therefore having C_s symmetry, is approximately 14.487 cm⁻¹ above Configurations 1 and 2 with C₁ symmetry.