Comment on “On the Longuet-Higgins phase and its relation to the electronic adiabatic–diabatic transformation angle” [J. Chem. Phys. <b>107</b>, 2694 (1997)]

We show that the new equation for nuclear motion obtained by Baer et al. is based on an invalid and self-contradictory approximation, and leads to incorrect results for the wave functions, energy levels, degeneracies, and matrix elements. Baer’s conclusion about the connection between the Longuet–Higgins (LH) phase and the adiabatic-diabatic transformation (ADT) angle is also shown to be incorrect. Applications of the method by Baer et al. are shown to contain further errors.