An exact kinetic energy operator for (HF)3 in terms of local polar and azimuthal angles

To facilitate exploiting the symmetry of (HF)3 we propose using local polar and azimuthal angles to specify the orientation of the HF units with respect to the frame of the trimer. We present and discuss the derivation of a kinetic energy operator in local polar and azimuthal angles and Pekeris-Jacobi coordinates