• A method similar to the previous but with the orientation of all molecular frames with respect to the reference equilibrium structure. The orientation is done by minimizing the mass-weighted functional i m i (r i -r e,i ) 2 , where i enumerates all the nuclei in the molecule, m are the masses and r are the coordinates of the nuclei, the index "e" denotes the reference equilibrium configuration of the nuclei. The minimization can be efficiently performed using the Kabsch algorithm. This way of computing the mean rotational constants is denoted as mean inverse inertia tensor oriented (MIITO).