Pseudomagnetic fields appear in the BornαOppenheimer method for molecules when conical intersections or electronic angular momenta are taken into account. These fields are not real magnetic fields but they have the same mathematical properties and can lead to real observable effects in the dynamics of molecules. A general Ε½ . vector potential gauge theory approach for including these field effects in the BornαOppenheimer method is introduced and applied to H q O scattering and the 2 Ε½ .
Ε½ . vibrational spectrum of Na X for zero total angular momentum J s 0 . The scattering 3 results for HO show significant shifts in the resonance energies and lifetimes due to a 2 ''magnetic solenoid''-type field originating from the C conical intersection in HO .
2 v 2
Significant changes in the state-to-state transition probabilities are also observed. The Ε½ . nondegenerate A and A vibrational spectra of Na X show significant shifts in the 1 2 3 energy levels due to a ''magnetic solenoid''-type field originating from the D conical 3h intersection in Na . These two examples show that the effects of pseudomagnetic fields 3 can be significant and in many cases they must be included to obtain agreement between theory and experiment. The newly developed gauge theory techniques for treating pseudomagnetic fields are also relevant for including the effects of real magnetic fields.