The Inversion-Torsion Potential Function for Hydrazine

The torsion-inversion potential surface for hydrazine has been determined from the rovibrational data using a new rotation-torsion-inversion Hamiltonian. All elements of the inverse moment of inertia tensor have been expanded into mixed Fourier series of large amplitude coordinates. That gives two major advantages: (i) no numerical integration is necessary at any step of calculation, and (ii) the three-dimensional integrals have been replaced by the products of one-dimensional integrals. It has been proven that the inversion-torsion coupling in hydrazine is negligible and the inversion-inversion coupling is very strong. The barrier to inversion of 2072 cm-1 is slightly higher than that in ammonia and the barrier to internal rotation of 934 cm-1 is relatively high but lower than that determined previously from one-dimensional models.