Fig. depicts the permanent dipole moments of the three MH diabats as a function of R. Note that the transition dipoles among the MH diabats are zero by definition (see Eqn. 9). As expected, the permanent dipole of the covalent state |C is flat as the electron density sticks to the transferring proton. On the other hand, the permanent dipoles of the |D and |A states are linear with respect to the position of the transferring proton as in these states the electron density is localized on the donor/acceptor atom such the permanent dipole is approximately